As children, many of our parents and teachers tell us something like: study hard in school, go to college, get a job, buy a house, settle down with a family, then retire. There are countless self-help books sold every year on how to live your best life. Influencers on social media are constantly sharing insights into their lives, and how you, too, can live as fulfilling of a life as they do (usually with the right skincare and exercise routines, diet, clothes, social life, travel, and so on). Ultimately, all of this boils down to trying to figure out what human flourishing looks like, and what it takes to get there.
2500 years ago, Aristotle also wondered what it is for human beings to live a good life. Before diving into his answer, think about what you think the ideal life for a human being is. How is it different from other (non-human) animals? What does it mean for a person to be living their best life?
Aristotle (384-322 BCE) was a Greek philosopher who studied under Plato and was one of the, if not the, most influential philosophers to ever live. Aristotle produced treatises on everything from zoology and astronomy to rhetoric, politics, and poetics. The Nicomachean Ethics presents Aristotle’s character-based moral theory–known as virtue ethics–and makes a case for what is required to flourish as a person.
Aristotle’s Nicomachean Ethics is split into ten books. In this article, we will focus on Book X, in which he argues the best life is the most complete life – a virtuous life of the mind, and that in order to achieve such a life, we need to think deeply about good things with others who do the same. If you want to start from the beginning, check out the Philosophy Teaching Library articles on Book I, Book II, and Books VIII and IV!
Eudaimonia: Often translated as ‘happiness’ (in this text) or ‘flourishing’, eudaimonia is the activity of living the best possible life for a human being. Eudaimonia is more than just feeling happy or contented – it’s the idea that there is a best way to live for human beings
Virtue: Virtues are cultivated tendencies to perform our function excellently, which allow us to reliably do the right thing, to the right extent, for the right reasons, given the demands of a specific circumstance. There are three components of virtues: virtues involve (a) skillful activity – they’re excellences after all!, (b) proper motivation, and (c) appropriate judgment – they often lead to judgments about what is the right thing to do, which requires careful attention to the circumstances
Pleasure: The enjoyable feeling that accompanies some activities. Some philosophers (but not Aristotle!) think that pleasure is the only thing that is good in itself
Endoxic Method: An argumentative structure that begins by laying out the endoxa, or the beliefs of the many or the wise, then raises apparent problems for those views and develops a resolution to those problems
Contemplation: The activity of human beings’ rationality. Contemplation is more than just thinking; it’s thinking excellently about ultimate truths. Contemplation is the ultimate activity associated with human flourishing
Aristotle often employs a particular argumentative structure, known as the endoxic method. This method starts by laying out the endoxa–the beliefs of the many or the wise, then raises apparent problems for those views and develops a resolution to those problems.
Book VII.1
And here we must follow our usual method, and, after stating the current opinions about these affections, proceed first to raise objections, and then to establish, if possible, the truth of all the current opinions on the subject, or, if not of all, at least of the greater number and the most important. For if the difficulties can be resolved and the popular notions thus confirmed, we shall have attained as much certainty as the subject allows.
Since the views held by the wise or the many probably have some truth to them, by beginning with those views and working to address the potential conflicts between them and problems with each of them, we should come out the other side of this process with a position that gets at the truth common to the endoxa while avoiding the problems of the endoxa. The last step of the method is to show how the ultimate position preserves the important parts of the endoxa, while avoiding the problems raised for the endoxa.
The first half of book X focuses on pleasure – the enjoyable feeling that we experience when we do certain things. Book X explores both whether pleasure is good, bad, or something in-between and the role pleasure plays in living a good life. After all, it seems like experiencing pleasure (feeling good) is a central part of being human, and both pleasure and pain play important roles in becoming a good person and living a good life.
Book X.1
Pleasure seems, more than anything else, to have an intimate connection with our nature; which is the reason why, in educating the young, we use pleasure and pain as the rudders of their course. Moreover, delight in what we ought to delight in, and hatred of what we ought to hate, seem to be of the utmost importance in the formation of a virtuous character; for these feelings pervade the whole of life, and have power to draw a man to virtue and happiness, as we choose what pleases, and shun what pains us.
In setting the stage for his endoxic method by considering what role the wise folks think pleasure and pain play in living well, Aristotle gives us a hint as to what he really thinks – there are appropriate and inappropriate pleasures (those we ought to delight in as opposed to those we ought not) and figuring out how to identify which is which is an important part of developing a good character. He also suggests that there is a close link between those activities we pursue and avoid and the cultivation of virtue.
Aristotle argues against pleasure as the ultimate good for human beings in response to Hedonists such as Eudoxus – those who believe pleasure is the ultimate good for human beings. While Aristotle’s arguments build towards his own account of the good life, a more modern philosopher, Robert Nozick, similarly argues against hedonism through his famous thought experiment, “The Experience Machine.” Find out more about Hedonism and Nozick’s Experience Machine here:
Of all of the positions Aristotle considers through the endoxic method, he almost always pays the most attention to his teacher, Plato’s.
Book X.2
“The pleasant life,” [Plato] says, “is more desirable with wisdom than without: but if the combination of the two be better, pleasure itself cannot be the good; for no addition can make the good more desirable.” And […] if any other thing be made more desirable by the addition of one of the class of things that are good in themselves, that thing cannot be the good. What good is there, then, which is thus incapable of addition, and at the same time such that men can participate in it? For that is the sort of good that we want.
Here, Plato informs us that a pleasurable life is a good one, but not the best life possible; for we can imagine a life of pleasure that could be better if we added something to it. As a result, there must be something good beyond pleasure. Aristotle accepts this line of reasoning, so this establishes part of our criteria for happiness – happiness is the thing that is so good, nothing can be added to it to make it more appealing.
Aristotle agrees with Plato that a merely pleasurable life is not the best life because the best life is a life of activity accompanied by pleasure. There are two additional problems.
Book X.4
[…] no human faculty is capable of continuous exercise. Pleasure, then, also cannot be continuous; for it is an accompaniment of the exercise of faculty. And for the same reason some things please us when new, but afterwards please us less. For at first the intellect is stimulated and exercises itself upon them strenuously, just as we strain our eyes to look hard at something; but after a time the exertion ceases to be so intense, and becomes relaxed; and so the pleasure also loses its keenness.
First, we can’t do things forever! We get tired and weak. Second, we get bored and don’t enjoy it as much! Psychologists in the 20th century coined the phrase the “hedonic treadmill” to capture the idea that we adapt to pleasurable things with increased exposure, so the more familiar we are with something, the less pleasure we take in doing it (the very point Aristotle is making here!). So what can we do? Is there anything humans can do, roughly continuously, that doesn’t eventually lose its novelty and pleasure?
If the ultimate good for human beings is something that cannot be improved, happiness would be the best possible activity – an activity that we always and continuously find pleasure in doing. Surely, though, some pleasures are good, while others are bad. Similarly, some things are pleasant to some people and unpleasant to others. How does this fit with happiness?
Book X.5
The pleasure which is proper to a good activity, then, is good, and that which is proper to one that is not good is bad: for the desire of noble things is laudable, and the desire of base things is blamable […] and the pleasures of the intellect are purer than these pleasures of sense[…]
[…] [Yet] what pleases this man pains that; what is grievous and hateful to one is pleasant and lovable to another. This occurs in the case of sweet things, too: a man in a fever has a different notion of what is sweet from a man in health; and a feeble man’s notion of what is hot is different from that of a robust man. And the like occurs in other matters also.
But in all matters of this kind we hold that things are what they appear to be to the perfect man.
Now, if this opinion is correct, as we hold it to be—if, that is, in every case the test is virtue, or the good man as such—then what appears to him to be pleasure will be pleasure, and what he delights in will be pleasant.
So the pleasures that matter in a good life are the pleasures that an ideal person finds pleasant. Just because one person enjoys hurting animals and another person enjoys volunteering at animal shelters, we don’t need to think that the pleasure of hurting an animal is just as important to a good life as the pleasure of helping an animal.
As we saw in X.5, Aristotle thinks that both good and bad activities can be pleasurable, but how would we know which pleasant activities are the good ones? One way we might try to identify which actions are the good ones is by appealing to the ideal person. Aristotle calls this person the phronimos. The phronimos is an idealized person who has all of the virtues and the sort of practical wisdom that enables them to perform the good activities in every situation.
Aristotle is not alone in thinking that having such an idealized figure to look to is helpful in thinking about virtue. The image of the sage appears in a number of additional virtue-frameworks including Stoicism and Confucianism. In fact, the Confucian philosopher, Mencius (or Mengzi – 4th century BCE), discussed the importance of the sage as a virtuous moral exemplar. Mencius’ sage and Aristotle’s phronimos differ in interesting ways, but in thinking about virtue more generally, they both agree that it’s helpful to consider exemplars!
If pleasure is not the ultimate good in life, then what is? In Book I, Aristotle began employing his endoxic method – he examined common beliefs about the best life, both from the wise and the many. He then argued from their ideas to a number of features necessary for a good, happy life. In X.6 he returns to those criteria.
Book X.6
We said that happiness is not a habit or trained faculty. If it were, it would be within the reach of a man who slept all his days and lived the life of a vegetable, or of a man who met with the greatest misfortunes. As we cannot accept this conclusion, we must place happiness in some exercise of faculty, as we said before.
But as the exercises of faculty are sometimes necessary (i.e. desirable for the sake of something else), sometimes desirable in themselves, it is evident that happiness must be placed among those that are desirable in themselves, and not among those that are desirable for the sake of something else: for happiness lacks nothing; it is sufficient in itself […]
So happiness is the exercise of some human ability, rather than just a habit or skill. Since someone asleep all the time or in a coma isn’t flourishing, happiness can’t be just a trait that you get and have; happiness has to be continuously engaged in. Additionally, happiness seems incompatible with someone who is really unlucky, so happiness is not merely a trained ability to do something; it’s got to be something that we actively engage in. Some things that humans actively engage in are things we do for the sake of other things. For example, working out is good for our physical and mental health, but it’s not the kind of activity that would be worth doing if it weren’t good for us. Unlike working out, happiness is worth having for its own sake.
Happiness is an exercise of some faculty, and exercising that faculty is good in itself. Since happiness is the ultimate good for a human being, happiness would be the activity of the best part of us. What’s the best part of us as human beings? Aristotle’s answer is our ability to reason, and the best form of reasoning is contemplation.
Book X.7
But if happiness be the exercise of virtue, it is reasonable to suppose that it will be the exercise of the highest virtue; and that will be the virtue or excellence of the best part of us.
Now, that part or faculty—call it reason or what you will […] is the faculty the exercise of which, in its proper excellence, will be perfect happiness. That this consists in speculation or contemplation we have already said. […]
This exercise of faculty must be the highest possible; for the reason is the highest of our faculties, and of all knowable things those that reason deals with are the highest.
Again, it is the most continuous; for speculation can be carried on more continuously than any kind of action whatsoever.
We think too that pleasure ought to be one of the ingredients of happiness; but of all virtuous exercises it is allowed that the pleasantest is the exercise of wisdom. At least philosophy is thought to have pleasures that are admirable in purity and steadfastness; and it is reasonable to suppose that the time passes more pleasantly with those who possess, than with those who are seeking knowledge.
Again, what is called self-sufficiency will be most of all found in the speculative life. The necessaries of life, indeed, are needed by the wise man as well as by the just man and the rest; but, when these have been provided in due quantity, the just man further needs persons towards whom, and along with whom, he may act justly; and so does the temperate and the courageous man and the rest; while the wise man is able to speculate even by himself, and the wiser he is the more is he able to do this. He could speculate better, we may confess, if he had others to help him, but nevertheless he is more self-sufficient than anybody else.
Again, it would seem that this life alone is desired solely for its own sake; for it yields no result beyond the contemplation, but from the practical activities we get something more or less besides action.
In order to show that his answer ultimately preserves the best parts of the endoxa, Aristotle returns to the criteria he laid out in X.1-6 for an account of happiness: [1] an activity, [2] continuously accompanied by pleasure, [3] that is self-sufficient (it cannot be improved by adding anything to it), [4] is valuable for its own sake, and as he adds here, [5] is the best exercise of the best part of us.
Does contemplation satisfy the criteria for happiness? Aristotle thought so! Contemplation is [1] an activity, [2] enjoyable, and we’re able to contemplate for much longer than we’re able to do other activities. A contemplative life requires basic necessities, but otherwise doesn’t require anything else. It may be that contemplation is better when we do it with others–after all, isn’t it better to discuss free will, morality, politics, the nature of the universe, and so on, with friends than it is to think about those on your own? We can think about big ideas in new ways, for longer, and enjoy it more with friends than we can on our own, but contemplation is still mostly [3] self-sufficient, especially compared to alternatives. Contemplation is also [4] valuable for its own sake, since it does not lead to anything other than itself. Finally, contemplation is the [5] best exercise of the best part of us – our ability to reason and grasp ultimate truths.
Having concluded that happiness is found in contemplation, Aristotle offers additional reasons for why we should think a life of contemplation is better than the alternatives.
Book X.7 (continued)
Again, happiness is thought to imply leisure; for we toil in order that we may have leisure, as we make war in order that we may enjoy peace. Now, the practical virtues are exercised either in politics or in war; but these do not seem to be leisurely occupations […], and, beside the practice of politics itself, it brings power and honours, or at least happiness, to himself and his fellow-citizens, which is something different from politics; for we [who are asking what happiness is] also ask what politics is, evidently implying that it is something different from happiness.
If, then, the life of the statesman and the soldier, though they surpass all other virtuous exercises in nobility and grandeur, are not leisurely occupations, and aim at some ulterior end, and are not desired merely for themselves, but the exercise of the reason seems to be superior in seriousness (since it contemplates truth), and to aim at no end beside itself, and to have its proper pleasure (which also helps to increase the exercise), and further to be self-sufficient, and leisurely, and inexhaustible (as far as anything human can be), and to have all the other characteristics that are ascribed to happiness, it follows that the exercise of reason will be the complete happiness of man, i.e. when a complete term of days is added; for nothing incomplete can be admitted into our idea of happiness.
Happiness connects with leisure, since (unlike things we do merely for fun) we work and go through difficult times in part so that we can enjoy our leisure time. In contrast, other (practical) virtues such as courage or temperance are relevant and exercised in politics and war – neither of which are leisurely contexts. If the options are a life of contemplation, the statesman (politician), or the soldier, and the statesman’s and soldier’s lives are not as enjoyable and otherwise do not fit our criteria for the good life, then the life of contemplation is happier than the alternatives.
Aristotle recognizes that a life where a person exercises virtues of courage, justice, temperance, and so on, is a good life; it’s just not quite as good as a life of contemplation. Why? In X.6, we concluded that happiness is self-sufficient. A person can only exercise virtues of courage or justice in contexts where there are other people living in a society, which means courage and justice are less self-sufficient than contemplation.
Book X.8 (continued)
Happiness, then, extends just so far as contemplation, and the more contemplation the more happiness is there in a life,—not accidentally, but as a necessary accompaniment of the contemplation; for contemplation is precious in itself. […]
But as we are men we shall need external good fortune also: for our nature does not itself provide all that is necessary for contemplation; the body must be in health, and supplied with food, and otherwise cared for. We must not, however, suppose that because it is impossible to be happy without external good things, therefore a man who is to be happy will want many things or much. It is not the superabundance of good things that makes a man independent, or enables him to act; and a man may do noble deeds, though he be not ruler of land and sea. A moderate equipment may give you opportunity for virtuous action (as we may easily see, for private persons seem to do what is right not less, but rather more, than princes), and so much as gives this opportunity is enough; for that man’s life will be happy who has virtue and exercises it.
Aristotle concludes that happiness perfectly overlaps with contemplation, and the more contemplation a person has in their life, the more happiness they have in life. Still, contemplation alone does not guarantee happiness; we also need to be healthy, have our needs provided for, and generally have things unfold in life without too much going wrong. After all, it’s hard to be happy (and to contemplate!) when we’re hungry, have a streak of bad luck, or are sick or injured. We also do not need to have a lot of material goods or power in order to be happy. In fact, it seems a lot of the time people with a lot of wealth and power are less likely to do good things with those resources than someone with a moderate amount of wealth and power! To be happy, then, we just need enough resources and opportunities to be able to develop and exercise virtues.
When we are trying to figure out how to live a good life, we are not just trying to get theoretical or abstract answers. Just knowing that we ought to be virtuous, or that happiness is found in contemplation, is not enough. We have got to actually work each day to become virtuous. As we’ve seen, many of the virtues depend on other people, and the way society is set up can make it easier or harder for us to cultivate virtues and live a good life. That means our ability to become better people and live better lives is deeply wrapped up with how good our society and its people are. Accordingly, Aristotle suggests we have two complementary options for making everyone’s lives better: education and politics. Both deeply influence the development of people’s character, feelings, reasoning, and actions.
Book X.9
As for theory or instruction, I fear that it cannot avail in all cases, but that the hearer’s soul must be prepared by training it to feel delight and aversion on the right occasions, just as the soil must be prepared if the seed is to thrive. For if he lives under the sway of his passions, he will not listen to the arguments by which you would dissuade him, nor even understand them. And when he is in this state, how can you change his mind by argument? To put it roundly, passion seems to yield to force only, and not to reason. The character, then, must be already formed, so as to be in some way akin to virtue, loving what is noble and hating what is base.
But to get right guidance from youth up in the road to virtue is hard, unless we are brought up under suitable laws; for to live temperately and regularly is not pleasant to the generality of men, especially to the young. Our nurture, then, should be prescribed by law, and our whole way of life; for it will cease to be painful as we get accustomed to it. And I venture to think that it is not enough to get proper nurture and training when we are young, but that as we ought to carry on the same way of life after we are grown up, and to confirm these habits, we need the intervention of the law in these matters also, and indeed, to put it roundly, in our whole life. For the generality of men are more readily swayed by compulsion than by reason, and by fear of punishment than by desire for what is noble.
Education is meant to bring a person to appreciate and enjoy the things they ought to enjoy, and be pained by those things that they should be pained by. As a result, their character can be shaped to respond to reason and goodness.
Education alone is not enough, though. Politics is there to ensure that those who develop good character continue to have that good character reinforced by society and its laws. Additionally, politics establishes laws for those who are not internally motivated to be virtuous, or generally those whose education did not succeed in developing good character. Most people are more responsive to fear and threats of punishment than they are to reason, so laws and punishments help people at very least avoid behaving viciously.
Book X.9 (continued)
It would be best, then, that the regulation of these matters should be undertaken and properly carried out by the state; but as the state neglects it, it would seem that we should each individually help our own children or friends on the road to virtue, and should have the power or at least the will to do this.
[…] Moreover, in spite of what has just been said, individual treatment is better than treatment by masses, in education no less than in medicine. As a general rule, repose and fasting are good for a fever patient, but in a particular case they may not be good. A teacher of boxing, I suppose, does not recommend every one to adopt the same style. It would seem, then, that individuals are educated more perfectly under a system of private education; for then each gets more precisely what he needs.
And so I think that he who wishes to make men better by training (whether many or few) should try to acquire the art or science of legislation, supposing that men may be made good by the agency of law. For fairly to mould the character of any person that may present himself is not a thing that can be done by anybody, but (if at all) only by him who has knowledge, just as is the case in medicine and other professions where careful treatment and prudence are required.
It would be great if the government could pass laws ensuring that everyone developed virtues and avoided vices, but that’s no guarantee either. After all, laws aim for bettering society as a whole, and are supposed to apply to everyone equally. Yet given how different each person is from the next, character education is much better when it’s specifically geared toward individuals than when it’s a generic one-size-fits-all. That means where politics fails in making people better, the burden of helping each person in a community become better falls on each of us individually. So in making people better, we need to keep in mind both what is generally good for all people in balance with what is good for a particular person.
Aristotle suggests education and laws should be used to make people better, but some might interpret Aristotle as saying education and laws should dictate right and wrong, what to believe, what to enjoy, and exactly how to behave. The idea that education and laws should shape people’s beliefs, values, and actions is often paired with worries about indoctrination, manipulation, or paternalism. Is an educational or political system aimed at making people better automatically a form of indoctrination or manipulation?
To reflect more on how you think education, law/politics, and living a good life relate to one another, write down 3-4 values that you believe are most important when you think about each of those topics. Examples of values include: freedom, fairness, equality, care, opportunity, tradition, security, dignity, justice, harm prevention, cultural identity, faith, the common good, and so on.
Once you’ve got your list of 3+ values of education, 3+ values of law/politics, and 3+ values of living a good life, see what values might be in tension with one another. For instance, freedom may be in conflict with security or equality, fairness may have tensions with care. Since contemplation is better with friends, ask others in your life what their value-lists would be and how they understand those values. Who knows, you might learn something–no indoctrination necessary!
In the final book of The Nicomachean Ethics, Aristotle finally answers the question he set out to answer at the start of Book I: What is the good life for a human being? Having developed a number of criteria for a proper account of human flourishing, he concludes that a life of contemplation is the best one to live. A close second, however, is the life of a morally virtuous person. Importantly, the good life depends on a number of factors outside of a person’s control, such as luck, their upbringing, the laws in the society in which they live, and their access to basic goods. While this book seeks to understand what it is for a human being to flourish, there is still work to be done understanding how politics can help (or hinder!) the flourishing of a society’s people. Fittingly, Aristotle’s Politics picks up where the Nicomachean Ethics X leaves off!
Interested in how we got here? Start from the beginning reading the entirety of The Nicomachean Ethics. Check out, too, the 1,000-word Philosophy article introducing Virtue Ethics.
The passages included in this section have been adapted from The Nicomachean Ethics, a book from eCampusOntaio’s Public Domain Core Collection. This work is in the public domain. All images were created using Midjourney. Thank you to the editors, anonymous reviewer, and Dr. Kristopher Phillips for the helpful feedback in improving this essay.
Finley, Cassie 2025. “Living Your Best Life: Aristotle’s Nicomachean Ethics, Book X.” The Philosophy Teaching Library. Edited by Robert Weston Siscoe, <https://philolibrary.crc.nd.edu/article/living-your-best-life>.
Contemplation: The activity of human beings’ rationality. Contemplation is more than just thinking; it’s thinking excellently about ultimate truths. Contemplation is the ultimate activity associated with human flourishing.
Eudaimonia: Often translated as ‘happiness’ (in this text) or ‘flourishing’, eudaimonia is the activity of living the best possible life for a human being. Eudaimonia is more than just feeling happy or contented – it’s the idea that there is a best way to live for human beings.
Virtue: Virtues are cultivated tendencies to perform our function excellently, which allow us to reliably do the right thing, to the right extent, for the right reasons, given the demands of a specific circumstance. There are three components of virtues: virtues involve (a) skillful activity – they’re excellences after all!, (b) proper motivation, and (c) appropriate judgment – they often lead to judgments about what is the right thing to do, which requires careful attention to the circumstances.
Pleasure: The enjoyable feeling that accompanies some activities. Some philosophers (but not Aristotle!) think that pleasure is the only thing that is good in itself
Endoxic Method: An argumentative structure that begins by laying out the endoxa, or the beliefs of the many or the wise, then raises apparent problems for those views and develops a resolution to those problems.
The Problem of Induction: A problem for reasoning about the future based on past experiences. How can we be justified in believing that patterns of events in the past will continue into the future?
A Priori: Hume is using the term ‘a priori’ to denote the kind of reasoning that allows one to gain knowledge as relations of ideas—in other words, reasoning from one necessary, definitional truth to another.
Justification: the concept of justifying one’s thinking, or one’s beliefs, is important in epistemology. Roughly, one’s thinking or belief is justified when there is good reason for it, or when it is well supported or well evidenced. All of these are ways of referring to some connection between what we think or believe and what is, or to some way of at least making ourselves think that we are closer to the truth.
Inference: The psychological process of moving from one thought to another, such as moving from the thought “it’s raining, and I don’t want to get wet” to “I should get my umbrella”, or from “I am tired, and it’s getting late” to “I should get some sleep”. Nowadays, philosophers tend to use the term ‘inference’ to mean the same as ‘reasoning’, and tend instead to use the term ‘association’ to refer to movements between thoughts that are not based on any logic or evidence.
Matters of Fact: Knowledge that is gained by experience, such as by observing or experimenting with objects in the world. For example, knowing whether all swans in the world are white requires somebody to examine the many swans in the world and make sure they do not happen to discover a black one (and in fact, there are black swans!).
Relations of Ideas: Knowledge that is gained just by sufficiently clear thinking, without having to observe or experiment with objects in the world. For example, knowing that a triangle has three sides is something you can know just because of what it means to be a triangle, hence without having to carefully examine triangular objects that you find throughout the world.
Reasoning: Developing arguments to try and support the truth of one’s beliefs.
Causation: A relation between events, where one event (cause) is responsible for another (effect). Eating too much chocolate can cause the effect of having an upset stomach, and not getting enough sleep can cause someone to be grumpy.
Epistemological Theories: Theories about the nature and possibility of knowledge – whether, when, how, and to what extent we can know about reality, such as the physical world, or our own consciousness. For example, one epistemological theory says that we can gain understanding of our own consciousness by studying the brain, whereas other theories say that we can only gain knowledge of consciousness by reflecting on our own inner experiences.
Aristotle means “happy” in the sense of a person who has developed a complete character, lived a full life, and become a true example of human goodness.
Happy Person – Someone who has developed her entire self well and lived a complete and flourishing life. She is a real and positive example of how we should live.
This is where Aristotle defines virtuous friends. These are friends who you actually answer the phone for. These are the friends who you ask for advice on work, love, and life. They are the friends that celebrate you for being you, but they also tell you when you’re messing things up. Not only do they love you, but you love them and try to be the same kind of friend to them too.
This is where Aristotle defines pleasurable friends. These are your TikTok, Snap Chat, or Instagram friends, the ones you post to social media when you’re having a good time.
This is Aristotle’s explicit definition of useful friends. These are your LinkedIn friends, those who you like networking with at events or enjoy working with on projects.
Virtuous Friendship – A friendship where people set as their goal for their friendship becoming good people together and living happy lives just because they value the good of their friends as persons. These are also known as “perfect” or “true” friendships. They are usually between people who are equally good. And they might be limited to people of equal social status, wealth, and power. Aristotle doesn’t think that any happy person will lack virtuous friends. But he thinks it’s likely that we’ll only have a few of this sort.
Pleasurable Friendship – A friendship where people set as their goal for their friendship some pleasant goal, such as friendship between people who go out on the town together. These friendships are plentiful and easy to form and dissolve.
Useful Friendship – A friendship where two people set as their goal for their friendship some useful or utilitarian purpose, such as friendship between work colleagues. These friendships are plentiful and easy to form and dissolve.
Aristotle uses “friend” broadly for any relationship between people who like each other, wish good things for each other, and get something out of spending time together.
Friendship – A relationship between two people who like each other, generally wish each other well, and have a goal for their interactions.
Happiness – The final end and highest good of human life. The perfect good that objectively fulfills human nature and subjectively satisfies desire.
Happiness Criteria – The conditions that the true object of happiness must satisfy. They are: finality, intrinsic value, purity, internality, authenticity, stability, self-sufficiency, completeness.
Object of Happiness – The thing in which happiness essentially consists, the attainment of which will make us truly happy.
Highest Good – The greatest good for a human being.
Final End – The ultimate goal of human life. All of our other goals are chosen for the sake of this final end.
Constituent Principles – Parts of a material object that cause the object to be the sort of thing that it is, but that cannot be removed from that object (in the way that some properties can be gained or lost). For Aquinas, this would include things such as form (the structure of a material object) and matter (that which is structured). For example, Dylan’s form is his soul, and his matter is his body. His soul and body are distinct, but Dylan could not exist if he were not composed of both.
Accident/accidental property – A property that something can possess or not possess while still remaining the thing that it is. For example, Dylan could grow taller, or he could stop being musical, without becoming a different person. By contrast, rationality is an essential property of Dylan, since being rational is part of the “what it is to be” of a human being.
Subject/Suppositum – Something or someone that can bear properties but is not itself a property that something else can bear. Dylan can have properties, like being short or being musical, but no one can have Dylan as a property.
Property – A feature that an object has. For example, a ball could be orange, which means that the ball has the property of orangeness. In many cases a property can be gained or lost. The ball could be painted green, in which case it would gain the property of greenness and lose the property of orangeness.
Actuality – The being, or act of being, of a thing. For example, hot water is actually hot (the water is hot), even though it is potentially cold. Likewise, a boy is actually a human being (he is a human being), even though he is also potentially a full-grown man (and he will still be an actual human being when he becomes a full-grown man).
Potentiality – Ways a given thing can become different from the way it is now. For example, cold water is potentially hot, since it can be heated up, and an acorn is potentially an Oak tree since it can grow to full size under the right conditions.
Essence – The “what it is to be” of a thing. For example, the essence of a human being is to be a rational animal, and the essence of a cheetah is to be the fastest land animal.
Principle of Specialization – The idea that work is more efficient and more effective if each worker specializes in exactly one task.
Extrinsic Value – Value a thing has that is dependent on something else. Extrinsically valuable things are worth pursuing because they get you something else that is valuable. Money, for instance, is only useful because it can be exchanged for other things.
Intrinsic Value – Value a thing has independently or inherently. Intrinsically valuable things are worth pursuing for their own sake.
Adeimantus and Glaucon were Plato’s older brothers (along with an older sister, Potone). They were both honored for military valor at a battle with Megara. We know little about their lives otherwise. Potone had a son, Speusippus, who inherited leadership of the Academy upon Plato’s death.
Thrasymachus was a real person, who lived about 459-400 BCE moved to Athens from Chalcedon to become a sophist (a professional teacher and public speaker). Only a few fragments of his work survives
Prudence – Prudence is virtue wherein a person is able to choose, in any given situation, the course of action that will lead to greater happiness. For example, a prudential person knows when it is appropriate to continue a difficult conversation and when it is best to wait for a more appropriate time.
Pleasure – Epicurus would have us think about pleasure as coming in two forms: moving and static. Moving pleasures are the type that we experience in the process of satisfying a desire (this coffee tastes amazing!). Static pleasure is the feeling of being satisfied — no longer experiencing need or want (I am feeling so peaceful sitting in the park). Epicurus thinks these static pleasures are the best sort.
Epicurus believed that reality is composed of matter. This sets him apart from other philosophers of the time who, often influenced by Plato, believed that reality is composed of both the material and immaterial (like the soul, or the Platonic forms).
Happiness – Epicurus uses the Greek word “eudaimonia,” which is typically translated into English as “happiness.” Whereas today happiness is most often used to describe a momentary feeling (this new notebook makes me happy!) Epicurus means something more like a consistent state of well-being and contentment.
Unconditioned: an ultimate explanation of reality. For example, if I explain why it is raining today by appealing to some atmospheric conditions, I can always ask for the cause of those conditions, and so on. Only a cause that is not caused by anything else (something unconditioned) would give us an ultimate explanation.
Transcendental Idealism: Kant’s mature philosophical position. It holds that appearances are not things in themselves, but representations of our mind. It is opposed to transcendental realism, which identifies appearances with things in themselves.
Appearances (vs. things in themselves): things as they are experienced by us (also known as phenomena). They should be distinguished from things as they are independently of our experience (things in themselves or noumena).
Metaphysics: the study of what there is. Traditionally, metaphysics is divided into general metaphysics and special metaphysics. The former investigates the general features of reality and asks questions such as ‘What is possible?’. The latter studies particular kinds of being and asks questions such as ‘Does God exist?’ or ‘Is the soul immortal?’.
Reason: the faculty that knows a priori. Kant uses this term in a general sense (the knowing faculty as such) and in a specific sense (the faculty that demands ultimate explanations).
A priori: term denoting propositions that can be known independently from experience. For example, propositions such as ‘All bachelors are unmarried’ or ‘The whole is greater than its parts’ can be known without recourse to any experience.
Make sure not to think that ‘unjustified’ means ‘false.’ Even if they are true, the point is just that this would not be something that had been shown.
‘Absolute’ might be a confusing word, here. Socrates means that the geometers are not reasoning about their drawing of the square, for example, but of the square itself. They do not conclude that, for the square they drew, the area is equal to the square of a side – they conclude that this is true for squares as an intelligible object, or, as Plato would say, the Form of the square.
By ‘science’, Plato means to be talking about all rational disciplines, including mathematics.
The form of the beautiful has to be perfectly beautiful because all instances of beautiful things are explained by it, so it has to be responsible for the highest possible degrees of beauty possessed by anything. Moreover, it has no trace of ugliness in it.
The form of the beautiful has to be immaterial because all the many beautiful things do not share any material – that is, they are all made of different stuff.
Form (εἶδος / ἰδέα) – Intelligible, immaterial, perfect entities that explain the unity among the many things which share the feature named by the entity (e.g., Beauty, Squareness, Oddness). For example, think of a square. There might be many different squares, but they all share features like having four sides of equal length. So, the Form of Squareness would include all of those features that make something a square.
Guardian – This is the name Plato gives to the ruling class in his ideal city. Think of them as philosopher kings – they have complete control over the organization of the state. The Republic is partially about why Plato thinks they would be needed for an ideal system of government and what they would need to learn to do the job well.
Plato has previously argued that we are made up of different parts. The first part is the appetitive which is responsible for our desires for food, sex, and other bodily needs. Then there is the spirited part, which longs for fame and honor. Finally, he identifies the rational part, which discerns what is good and bad for us through reason. The parts can all come into conflict with one another, and managing their relations is what Plato thinks justice is all about.
Soul (ψῡχή) – What Greeks meant by this word is controversial. For now, think of it as the thing that makes you different from a rock or other objects, the thinking and experiencing part of you as well as the part of you that acts and makes decision. You might use the word ‘mind’ or ‘self’ to talk about this.
Virtue – Virtues are the character traits that make a person good. For example, most people consider courage and generosity to be virtues. English-speakers usually reserve the word ‘virtue’ for human beings, but in ancient Greek the word can be more comfortably applied to other beings as well.
Was it his burly physique, his wide breadth of wisdom, or his remarkable forehead which earned him this nickname?
Aporia – A Greek term for “being at a loss” or “clueless.” Socrates often questions people until they have no idea how to define something that they thought they understood.
You might be confused by the word ‘attention’ below. In Greek the word is therapeia, from which we get the English word ‘therapy.’ It primarily means the same as ‘service’ as in ‘to serve,’ but shades into ‘worship,’ ‘take care of,’ and ‘attend to.’
Meletus – A poet and citizen of Athens and one of Socrates’ accusers. Amongst other things, Meletus accused Socrates of impiety and corrupting the youth.
Divine Voluntarism – The idea that God is free to determine even the most basic truths. If divine voluntarism is true, then God could have made it so that 2+2=5 or so that cruelty and blasphemy are holy and good.
Euthyphro Dilemma – The question, “Is a thing holy because the gods love it, or do the gods love it because it is holy?” The general idea of a forced choice (or “dilemma”) about the true order of explanation occurs often in philosophy and gets referred to by this term.
Essence – What a thing fundamentally is. A square might be red or blue without changing the fact that it’s a square, but a square must have four sides, so having four sides is part of a square’s essence.
Definition – The perfect description of a thing. A definition should pick out all and only examples of a thing. For example, ‘bachelor’ might be defined as ‘unmarried man,’ because all unmarried men are bachelors, and only unmarried men are bachelors.
In Disney’s retelling of the Hunchback of Notre Dame, the clergyman Claude Frollo orders the death of many Roma on religious grounds. It is clear, however, that he is really motivated by spite and his unrequited lust for the Romani woman Esmerelda.
Spanish conquistadors were shocked by the scope of ritual human sacrifice among the Aztecs, as hundreds or even thousands of people were sacrificed each year. The Aztecs thought that the sacrifices could repay the sacrifices the gods had made in creating the sun and earth.
Zeus – The god of sky and thunder in ancient Greek mythology, Zeus was depicted as chief among the gods and called the father of the gods and men.
Forms – The perfect, divine, and intelligible entities that exist independently of the physical world. They are comprehensible only through reason, not through our senses, and their existence explains the properties of objects in the physical world.
Recollection – The soul existed prior to birth; during this time it learned everything, and hence all learning is only recalling what we already know.
Immortality of the Soul – Unlike the body, the soul is not subject to physical death, because it is immortal and indestructible.
Philosophy – The practice of preparing the soul for death by training it to think and exist independently of the body
Death – Plato understands this as the soul’s separation from the body
Human Identity Across Time – Locke’s notion that any human stays the same across time if, and only if, it maintains the same (distinctively human) organizing structure of parts.
Substance Identity Across Time – Something is the same substance across a segment of time if, and only if, it continuously exists across the relevant segment of time without gaining or losing any of its parts.
Immaterial Soul – A personal thinking substance without any physical constitution.
Personal Identity Across Time – Whatever makes someone the numerically same person (i.e., that very person) at different times; according to Locke, it is a relation of first-person consciousness via memory.
Person – Locke’s forensic definition of person (pertaining to courts of law regarding the justice of praise, blame, reward, or punishment): a thinking, intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing in different times and places.
The Prophet Muhammad is a central figure in Islam. He is viewed as the last of a long line of prophets, which includes Moses and Jesus. He is responsible for writing the Quran, which was dedicated to him by the angel Gabriel. His life and sayings are recounted in the Hadith; he is viewed as an exemplary role model of Islamic life and faith.
Exhortation — The method of understanding and interpreting Truth available to the common people. The majority of people take scripture literally and understand truth and right action based upon this understanding. They are persuaded by the vivid imagery of the Quran and the rhetorical exhortations of religious leaders. Averroes takes this to be lowest form of understanding
Dogmatic Discourse — The method of understanding displayed by those who, through natural ability and habit, are able to have a deeper understanding of the Quran, and of the truths it illuminates. These people know that not all of the scriptures are to be taken literally, and that greater underlying Truths are revealed by interpreting some elements allegorically. Still, they err on the side of dogmatism and literal interpretation whenever uncertainty arises. Averroes associates this way of thinking with Muslim theologians and views this to be the middle level of understanding.
Philosophical Inference – The type of understanding associated with philosophical demonstration or argument. This is the highest level of understanding, accomplished by a select few, who have a natural capacity for philosophy and proper philosophical training.
Law — The Quran (the central religious text of Islam) and, to a lesser extent, the Hadith (reports of what the prophet Muhammad said and did). Averroes is concerned with explaining how philosophy relates to what Muslims take to be the unerring Truth regarding God and the nature of existence, as they are expressed in Scripture.
Occasionalism — a theory claiming that God is the only true cause of changes in the world. For example, when you high-five me, you’re not really the cause of the stinging sensation I experience. God is the cause. Your high five is just the occasion on which God causes it.
Interactionism — a theory claiming that things in the world can truly cause changes in each other. For example, when you high-five me, you truly cause me to experience a stinging sensation in my hand.
Substance Dualism — a theory claiming that the mind (or soul) and body are two distinct and very different things.
Body — what it sounds like! The body is the physical part or aspect of a thing and has characteristics like shape, size, etc.
Soul — that part or aspect of a thing involving mental aspects of their existence, e.g., thoughts, feelings, decisions, etc. The “soul”, in this sense, is more or less just the mind.
Causal Interaction — When one thing acts (i.e., itself does something) and in so acting makes another thing change. For example, when you high-five me, you cause me to experience a stinging sensation in my hand.
God as God – The phrase “God as God” is basically a synonym for “God the subject.” In other words, it refers to God precisely in God’s status as an incomprehensible divine Other.
Incarnation – The Christian doctrine of the incarnation is the notion that the word of God became fully human in the person of Jesus of Nazareth. It is closely associated with the doctrine of the trinity, which asserts that God the Father, God the Son (Jesus as the word made flesh), and God the Holy Spirit are one God.
Religious Fanaticism – In Feuerbach’s use of the term, a religious fanatic is someone who is unwaveringly faithful to God as an utterly mysterious superhuman being. They subordinate other things—especially the love of other humans—to submission before this divine other.
God the Subject – When Feuerbach refers to God as a subject, he is referring to the commonplace religious belief that God is a being who has various attributes, like a loving nature.
Faith Separates Man From God – Faith separates God from man in this sense: it treats God as a mysterious other, a being radically distinct from us.
Faith – Belief in and fidelity to a transcendent divine subject like God.
Orthodoxy – Orthodoxy refers to “right belief,” and it is concern with identifying heresies and ensuring that people believe and practice correctly.
Indirect Form of Self-Knowledge – Feuerbach’s view is that religious belief is a naive way of relating to our human nature and its perfections. It is naive or childlike because it treats these as external realities that belong to God. He believes a mature and contemplative person realizes these don’t belong to God, but rather to our species, abstractly conceived.
Above the Individual Man – The human perfections are “above the individual” insofar as no particular individual ever perfectly realizes them. They are abstractions.
Divine Trinity – Feuerbach is having fun here. He is using the theological phrasing of the Trinity to talk about human perfections. In calling reason, love, and freedom of the will “divine,” he means they are absolutely good; they are activities whose goodness is intrinsic to their practice or exercise. This isn’t a novel philosophical view. For example, Immanuel Kant argued that autonomy or a good will is the only thing which is unconditionally good.
Perfections – The end to which a faculty or power is ordered. For example, omniscience would be the perfection of the intellect. Traditionally, God is said to possess all perfections.
Love – When Feuerbach writes about love, he is referring to unconditional concern for others and the desire for fellowship with them. He is here asserting that love, understood in this sense, is the perfect activity of the affective faculty. In other words, our feelings and passions are fully actualized and engaged in an intrinsically valuable activity when we genuinely love others.
Infinite – The infinite is whatever can be understood as unbounded or unlimited. Human nature in the abstract is unbounded and unlimited. It is only bounded or limited in its concrete form as it is realized by particular material individuals.
Higher Consciousness – The sort of consciousness that mature human beings possess, but which other animals do not. It is “higher” than animal consciousness because it involves thinking abstractly about the form or essence of things.
Science – Feuerbach uses the term science in its classical sense, meaning systematically organized knowledge. Any body of knowledge founded on an understanding of first principles and the essences of things is a science in this sense.
Popular Sovereignty – The view that a government’s authority to rule comes from the people, making a ruler subject to the will of their citizens.
The Divine Right of Kings – The theory that kings are chosen by God and thus that political revolt is a rebellion against the will of God.
Synthesis – The prefix ‘syn-’ means “together,” so a synthesis “brings together” or combines elements of both a thesis and its antithesis.
Antithesis– An antithesis is the contradiction of a thesis. For example, internationalism could be understood as the antithesis of nationalism.
Thesis – In Hegelian terms, a thesis can be understood as a position or theory. Examples include any of the “-isms” that we discuss in science, history, and philosophy, such as Darwinism, capitalism, nationalism, etc.
Progressor’s Temptation – a unique temptation for those making progress in which pride impedes their further progress and leads to backsliding.
Progressors – those who are not yet expert Stoic practitioners, but who are also aware of the fact that they must change their lives in that direction. They are working on making progress.
Intellectualism – the philosophical view that our motivations and emotions are all judgments. The reason why you do something, your motivation, is because you believe it’s the right thing to do. The reason why you feel good or bad about something, an emotion, is because you believe that something good or bad happened to you.
Duties – acts of service, obedience, and respect that we owe to each other. The duties we owe to each other depend on what kind of relationship we have.
Askeses – exercises of Stoic thought and practice that make the lessons and habits of Stoic philosophy second-nature for Stoic practitioners.
Externals – things that are not under our control but that are all-too-easily confused with things that should be important to us, like wealth, status, and pleasure. Too many people believe externals like these are necessary for the good life, and the Stoic path is to focus not on these things but rather what is up to us.
The Fundamental Division – the division between things that are under our direct control and those that are not. The important lesson is to care only about the things we can control.
The Greatest Happiness Principle – A principle which says that actions are right insofar as they promote happiness and wrong insofar as they promote unhappiness
Higher and Lower Pleasures – Types of pleasures that differ in terms of their quality. Things like food and drugs create lower pleasures. Things like intellectual pursuits and doing the right thing create higher forms of pleasure.
The Doctrine of Swine – An objection that utilitarianism entails that if people would be happy rolling in mud, that’s what would be morally best for them to do, so we should reject the theory.
Utilitarianism – A normative theory of which actions are right or wrong. Utilitarianism says the right action is that which maximises utility.
Jeremy Bentham – Considered by some as the father of utilitarianism, Bentham was a moral philosopher and one of John Stuart Mill’s teachers
Epicurus – an ancient Greek philosopher and one of the first to advocate that the ultimate good is experiencing pleasure and avoiding pain.
Utility – The thing that is ultimately valuable in itself. For Mill, this is happiness, which he then understands as pleasure and the absence of pain.
Contract Theory – a modern political theory identifying consent as the sole justification for government. Contract theory is associated with Thomas Hobbes (1588-1679), John Locke (1632-1704), Jean Jacques Rousseau (1712-1778), and more recently, John Rawls (1921-2002)
Prejudice – a foundational, strongly held, unreasoned (but not necessarily irrational) moral opinion or belief. We might believe, for example, that parents have special obligations towards their own children.
A Priori – a philosophical term of art meaning (in Latin) “prior to experience,” which refers to knowledge that is innate or arrived at purely through reasoning, like the truths of mathematics.
Rights – moral claims invoking immunity from (or entitlement to) some specific treatment (or good) from others. Commonly recognized rights include the right to free speech or the right to healthcare.
Reform – a change in the social order that originates from the existing character of society. An example would be market-based healthcare reform in a capitalist society.
Conservatism – a modern political ideology that aims to preserve and promote the existing (or traditional) institutions of society. These institutions typically include the rule of law, property, the family, and religion.
Contingent Being – A being that can fail to exist. Its existence is not guaranteed. This being might come to exist or it might not.
Necessary Being – A being that can’t fail to exist. Its non-existence is impossible. This also means that such a being has always existed.
Want to read more about why the infinite regress option doesn’t work in the Second Way? Check out Sean Floyd’s entry in the Internet Encyclopedia of Philosophy.
Efficient Cause – An efficient cause is something that directly makes another thing exist or move. An example of this is when I kick a ball down a hill. I am the efficient cause of the ball rolling down the hill because I make it move down the hill.
Infinite Regress: Begin with some fact. We begin to explain that fact by appealing to another fact, where these facts are related by either causality or dependence. To create the regress, you keep appealing to more and more facts about causality and dependence without end.
Actuality – An ability or action something is currently exercising. Imagine that I am sitting comfortably at my desk, and then I stand up to take a break from reading. In this case, I am now actually standing.
Potentiality – What something has the capacity to do, but isn’t currently doing. Imagine I am sitting comfortably at my desk. Even though I’m not currently standing, I have the capacity to be standing. So, even while I’m not standing, I have the potential to stand.
Theists and Non-Theists – A theist is someone who believes that God exists, while a non-theist does not. Non-theists include atheists, who believe that God does not exist, and agnostics, who are uncertain about whether God exists.
Glaucon – one of Plato’s brothers and one of Socrates’ main interlocutors in the Republic dialogue. In that dialogue, he challenges Socrates to provide a compelling justification for why one should be a just person beyond merely following conventions or avoiding punishment. This sets up Socrates’ defense of justice as intrinsically worthwhile. Throughout the Republic, Glaucon prods Socrates to fully explain his theories of the ideal society, philosopher-kings, and the Form of the Good.
Aristotle – a Greek philosopher (384-322 BC) who studied under Plato and went on to be one of the most influential philosophers to ever live. Simply called “The Philosopher” by Thomas Aquinas and others in the medieval period, Aristotle’s views would eventually be synthesized with Christian theology, laying the intellectual foundation for later scholarly developments in Western Europe.
Understanding – Socrates describes education as turning one’s “understanding” in the right direction. The word “understanding” here translates the ancient Greek term “to phronēsai,” which means “understanding,” “being conscious,” or “having insight.” People who are wicked focus their “understanding” on how best to accomplish their selfish and narrow desires. Those who are wise, in contrast, have learned to focus their “understanding” on what is truly good and beneficial.
The Form of the Good – Socrates characterizes the ultimate goal of education as coming to know “the Form of the Good.” The Form of the Good is his technical term for the meaning of goodness: what it is to be good. Socrates is clear that this “knowledge of the Good” is not simply theoretical knowledge, but also knowledge in the sense of “knowing how”: knowing how to achieve what’s good, to do what’s good, to accomplish what’s good. Mere “book knowledge” or simply being smart is not enough.
The Intelligible – Socrates uses “the intelligible” to name the aspects of the world that we can only grasp through thinking or insight. With my eyes I can see the tree outside my window, but what it means to be a tree is something I can only comprehend in thought. Likewise, I can see the people around me, but human nature, human dignity, and what it means to be human is something I can only grasp conceptually. “The intelligible” is the world insofar as it “makes sense” and can be comprehended.
The Visible – By “the visible,” Socrates means those aspects of the world we can perceive with our five senses and our imagination—those aspects of the world we can see, hear, taste, smell, touch, and imagine. For example, with my eyes I can see the sky, trees, people around me, and so on as visible things. “The visible” is the world insofar as it can be perceived and imagined.
Education – Socrates says that the allegorical story he tells represents the effect of education on human nature. “Education” here is a translation of the ancient Greek word “paideia,” which means “education” in the widest sense of the term. “Paideia” doesn’t mean “education” in the sense of going to school or getting good grades. Instead, it refers to the process of becoming a wise, intelligent, good, and well-rounded human being.
Allegory – An allegory is a symbolic narrative where characters, events, and/or settings represent abstract ideas or convey deeper meanings beyond the literal story. Socrates tells such a symbolic narrative in the passages below. The characters, events, and setting of his narrative symbolize the effect of what he calls “education.”
Self-knowledge – Knowledge of the contents of one’s own mind, such as one’s own beliefs and desires. Self-knowledge can be gained through introspection, that is, by reflecting on what one thinks and experiences. Some philosophers believe that self-knowledge has special properties that our knowledge of the external world lacks, such as being clearer, more reliable, or more valuable.
Dualism – The view that the mind is entirely distinct from the body. This view is usually contrasted with different kinds of monism, which hold that the mind is ultimately just a part of the body (materialism) or that the body is ultimately just a part of the mind (idealism). Dualists hold that the mind and the body are fundamentally different aspects of reality, and both categories are needed to properly describe the universe, especially the human person.
The Self – What the ‘I’ in ‘I am, I exist’ refers to; the part of you that really makes you you. Many philosophers have provided rich accounts of what the self ultimately is, including the soul, the mind, one special feature of the mind (such as consciousness), a mixture of all these elements, or perhaps a mere illusion.
The ‘Cogito’ – Descartes’ famous claim ‘I think, therefore I am’ is often referred to as the cogito. The name comes from the Latin rendering of this phrase, which is ‘cogito, ergo sum.’ Descartes held that one can always believe this proposition with certainty. We cannot doubt our own existence, so the cogito survives his exercise of intense doubt. The cogito appears several times in Descartes’ writings, and he often phrased it slightly differently each time. It appears in the Second Meditation as ‘I am, I exist.’
Certainty – When one believes something with certainty, one is maximally confident that it is true. A certainty is something that is beyond dispute or immune to doubt. Although this captures the basic idea, like many epistemological notions, clarifying precisely what the notion of certainty amounts to is an ongoing area of philosophical research.
Vice – A bad habit that we learn over time through instruction or instinct and that we develop through repetition. What makes the habit bad is that, once we have that habit, our tendency is to do the incorrect thing in certain types of situations. We may choose to do something entirely uncalled for in that situation, or we may act at the wrong time, in the wrong way, to the wrong degree, or with the wrong attitudes, or for the wrong reasons.
Relative Mean – The “Goldilocks amount” of some type of action or emotion. When you act in this way, according to Aristotle, you act exactly as is required under the current circumstances. This means that you do what is called for by the situation at hand, rather than doing something too extreme or not doing something extreme enough. You do something in the moderate amount (the mean amount) relative to the specific situation you are in when you need to act.
Excellence/Virtue – A good habit that we learn over time through instruction and repetition. What makes the habit good is that, once we have that habit, we have a strong tendency to do the right thing at the right time, in the right way, to the right degree, with the right attitudes, whenever we are confronted with a situation that we know calls us to exercise that habit.
Doxastic Voluntarism – the view that we have at least some control over what we believe.
Evidence – information that increases the probability that a claim is true.
Sufficient – enough of something for a particular purpose. Whether something is sufficient is context-dependent.
Solon – In the Histories of Herodotus, Solon visits Croesus, the king of Lydia. Even though Croesus shows Solon all of his wealth, Solon refuses to call him the happiest man who ever lived because he does not know how Croesus will die
Priam – According to Greek mythology, Priam was the final king of Troy during the Trojan War. Despite his wealth and political power, he was killed by Achilles’ son Neopotolemus during the Sack of Troy
Virtue – The consistent and reliable tendency to perform one’s function excellently. When a person has a certain virtue, like courage, they have spent time developing the habit, in this case reacting to danger well, using their human abilities. The virtues then make it possible for us to live a life of flourishing
Sardanapalus – An Assyrian king described by the historian Diodorus as living a life of extreme decadence. Sardanapalus indulged himself with food, alcohol, and many concubines, even going so far to say that physical gratification is the purpose of life. Chrysippus said that, on his tomb is inscribed the following: “Though knowing full well that thou art but mortal, indulge thy desire, find joy in thy feasts. Dead, thou shalt have no delight […] I have only what I have eaten, what wantonness I have committed, what joys I received through passion; but my many rich possessions are now utterly dissolved.”
Function – the characteristic activity of a given thing which makes it what it is. The function of a knife is cutting, while the function of a heart is to pump blood
Eudaimonia – Frequently translated as ‘happiness’, eudaimonia means the attainment of active human flourishing, and is the end Aristotle identifies as humanity’s highest final good
Final Good – A good that we pursue for its own sake. Common examples of final goods include happiness, knowledge, and friendship
Instrumental Good – A good that we pursue for the sake of some other good. A common example is money, as money allows us to purchase other kinds of goods
Anytus – an Athenian politician, war general, and one of the primary accusers behind Socrates’ prosecution. Anytus feared that Socrates would undermine the young Athenian democracy he had helped create and defend
Oracle of Delphi – the high priestess at the temple at Delphi, the oracle was one of the most sought after seers of the ancient world and was thought to relay messages from the god Apollo
Chaerephon – an ancient Greek from the city Sphettus, Chaerephon is remembered as a loyal friend of Socrates, also making an appearance in two other Platonic dialogues, the Charmides and the Gorgias
Meletus – A poet and citizen of Athens and one of Socrates’ accusers. Amongst other things, Meletus accused Socrates of corrupting the youth
Apollo – the ancient sacred site Delphi was dedicated to the god Apollo, an ancient Greek god and the god that Socrates refers to throughout the Apology
Virtue – a character trait, acquired through habitual practice, that enables one to act well. The virtues can also be thought of as excellences of human character, as they make it possible for us to live a life of flourishing. Examples of the virtues include courage, prudence, and justice
The Evil Demon Argument – Argues that we cannot hold any of our beliefs with certainty because we could be radically deceived by an evil demon. A classic argument given by Descartes for doubting the reliability of almost all of our beliefs
Philosophical Skepticism – The position that we do not know many things that we ordinarily take ourselves to know
A Posteriori Knowledge – Knowledge that can only be acquired through having particular, concrete experiences. Such knowledge can be gained simply through our everyday experiences, or through more complex means like controlled scientific experiments
A Priori Knowledge – Knowledge that can be gained without having any particular concrete experiences. Such knowledge is typically gained by rational insight or intuition
Cartesian Method of Doubt – A process employed by René Descartes of rejecting all beliefs that he had at least some reason to doubt in order to see if he had any beliefs that he could know with certainty
Revelation – Theological truths that have been made known by means of some religious text, testimony, authority, or experience, or the act or process in which such truths are made known.
Rationalism – The view that the only reliable means of coming to know truths about God is reason. As a result, what we might otherwise believe by means of faith ought to be disregarded or even rejected in favor of what we must believe by means of reason.
Fideism – The view that the only reliable means of coming to know truths about God is faith. As a result, what we might otherwise believe by means of reason ought to be disregarded or even rejected in favor of what we must believe by means of faith.
Faith – The act of accepting a proposition as true for which there is less than demonstrable evidence, which rises above mere opinion but falls short of logical or scientific demonstration. Faith can also refer to a particular religious tradition or the body of beliefs that are central to that religious tradition.
Virtue – a character trait, acquired through habitual practice, that enables one to act well. The virtues can also be thought of as excellences of human character, as they make it possible for us to live a life of flourishing. Examples of the virtues include courage, prudence, and justice
Socratic Ignorance – an awareness of one’s own ignorance, and the reason that Socrates was deemed wise by the Oracle of Delphi. A person who lacks Socratic Ignorance may believe they know many things they actually don’t, leading them to overestimate how well they understand the world
Apology – a formal defense of justification of an action or belief. A Christian apologist, for example, is someone who defends their faith and seeks to justify it through an appeal to reason.
