Imagine that every person everywhere is playing the same multiplayer online video game, something similar to World of Warcraft, Elder Scrolls Online, or Star Wars: The Old Republic. The game is played from a first-person point of view, and the game’s virtual world is shared and interactive. I can see (virtual) you, talk to (virtual) you, and high-five (virtual) you, and it’s all perfectly coordinated. Of course, behind the scenes in online games like this, things are a bit more complicated. When you do something in the game, your computer communicates that information to the game’s central servers, and then these servers communicate this information to my computer, and then my computer generates and displays the changes from my (virtual) point of view. So, really, we never directly interact, even though it looks like it.
But this, of course, would just be a video game, right? In the real world, we directly interact with one another all the time, right? You say “What’s up?” to your friend, causing her to hear the sound of your voice. She high-fives you, her hand causing you to experience a small stinging sensation. These interactions appear to be instances of causation, or causal interaction. All this is so obvious and frequent that you may not have given it much thought.
But if you believe in an all-powerful and all-knowing God who created all of reality—as did Leibniz, as well as many other philosophers of his time and ours—is it possible that it’s actually God that causes all the changes in things, working unseen behind the scenes? Could it be that God is like the game’s central servers, with the appearance of interaction caused by an extremely precise pre-arrangement of all things, including you and me, like a cosmic dance of living and conscious wind-up toys, pre-destined to live and act in perfect harmony while appearing as if they’re really interacting? Leibniz considers several options for understanding what appear to be causal interactions, and, surprising as it might seem, he concludes that this option—this pre-established harmony—is the correct one. Why in the world would he think this? Read on!
Gottfried Wilhelm Leibniz (1646–1716) possessed one of the most towering and varied intellects in the history of western thought. His work in philosophy and mathematics were influential in his own time as well as today, but he was also a well-regarded scientist, lawyer, historian, and more. In philosophy, Leibniz’s contributions were diverse, but one of his best-known and most distinctive positions is the pre-established harmony, which is his big-picture explanation for the appearance of causal interaction in the world. If you didn’t think this appearance needed explanation, don’t worry, that will become clearer below.
Perhaps Leibniz’s best-known statement of his pre-established harmony theory appears in “A New System of Nature”, an article he published anonymously in 1695 in the Journal des savants, a prominent French academic journal of the time. Below, you’ll be reading selections from that article, and the full text can be found here.
When looking at Leibniz’s intellectual output, Denis Diderot, a prominent philosopher and intellectual born near the end of Leibniz’s life, wrote:
“When one examines oneself and compares [one’s] small talents with those of a Leibniz, it is tempting to throw away the books and to go die peacefully off in some ignored cranny.”
Substance — a thing that exists in its own right, as opposed to existing only parasitically on another thing. For example, your dog, Fido, exists in his own right, while Fido’s particular three dimensional doggy-shape exists only because Fido himself exists.
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.
Body — what it sounds like! The body is the physical part or aspect of a thing and has characteristics like shape, size, etc.
Substance Dualism — a theory claiming that the mind (or soul) and body are two distinct and very different things.
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.
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.
Page 76
I thought myself entering into port, but when I came to meditate on the union of the soul with the body I was as if cast back into the open sea. For I found no way of explaining how the body can cause anything to pass into the soul, or vice versa; nor how one substance can communicate with another created substance. Descartes gave up the attempt on that point, as far as can be learned from his writings […]
René Descartes (1596-1650)—another philosopher and mathematician whose theories were very influential both at the time of Leibniz’s writing and still today—believed in a theory called substance dualism. According to this theory, a person’s mind (or soul) and body are two distinct and very different things: every mind is a thing capable of all the various types of mental activity, while every body is an “extended thing”, i.e., a three-dimensional thing with a particular shape, size, etc. But despite all this, Descartes still believed that your mind and your body are in some way linked up to one another, so that your mind can cause changes in your body (e.g., your arm’s rising when your mind wills it) and vice versa (e.g., your mind’s feeling pain when your arm is poked). This basic understanding of mind-body causal interaction is called interactionism. But Descartes had trouble explaining how mind-body interaction could possibly occur. If mind and body have completely different natures, well, then how could they possibly interact, since they are nothing like one another? Descartes’s failure to give an explanation here is what Leibniz means by saying that Descartes “gave up the attempt”.
Try an experiment right now. Sit quietly. Focus. Now, intentionally raise your arm. Go ahead, raise that arm. Your arm rose, right? But how did that happen? That is, how did your mind cause a part of your body to move? The question isn’t just about signals sent from your brain to your arm. The question is about how your mind, or soul, communicated with your body.
Let’s try another quick experiment. Using your fingernail, or a not-too-sharp nearby object like a pencil, gently—only gently now!—poke your arm. You felt a sensation, right? It appears that a change in your body—in this case, a bit of force applied to your skin, and in turn to one or more nerves beneath your skin—caused your mind to experience a sensation. But how does that work? Again, the question isn’t about how the nerves in your arm transmit signals to your brain. The question is about how your body caused your mind to have a particular conscious experience.
Descartes might not have solved the problem of how the mind and body interact, but those who came after him offered alternative theories, and one of the most prominent of these is called occasionalism.
Pages 76-77
But [Descartes’s] disciples seeing that the common view was inconceivable, were of the opinion that we perceive the qualities of bodies because God causes thoughts to arise in the soul on the occasion of movements of matter; and when the soul wished to move the body in its turn they judged that it was God who moved it for the soul. And as the communication of motions again seemed to them inconceivable, they believed that God gave motion to a body on the occasion of the motion of another body. This is what they call the system of Occasional Causes which has been much in vogue on account of the beautiful remarks of the author of the Search After Truth.
By “Descartes’s disciples”, Leibniz is referring to those who accepted Descartes’s substance dualism concerning the mind and body, but who denied that the mind and body—or indeed any substances in the created world at all—could ever truly causally interact. Leibniz specifically mentions the philosopher and theologian Nicolas Malebranche, the author of Search After Truth, and perhaps the best known of this particular sort of “disciple” of Descartes.
According to these followers of Descartes, the occasionalists, when you high-five your friend, it’s not your hand or your friend’s hand that causes her mind to experience that stinging sensation. Rather, God directly causes her mind to have the stinging sensation on the occasion that your hand slaps hers. This same explanation applies to any seeming instances of causal interactions between things in the world. Moreover, these philosophers denied that any substances have any active causal power at all!
Leibniz agreed with the occasionalists that, despite appearances, no created substances could truly cause changes in each other. But he thought their theory had serious shortcomings.
Page 77
It is indeed true that there is no real influence of one created substance upon another, speaking in metaphysical strictness, and that all things with all their realities are continually produced by the power of God; but in resolving problems it is not enough to employ a general cause and to call in what is called the Deus ex Machina. For when this is done and there is no other explanation which can be drawn from secondary causes, it is, properly, having recourse to miracle. In philosophy it is necessary to try to give reasons by making known in what ways things are done by divine wisdom, in conformity to the idea of the subject concerned.
The Latin phrase “deus ex machina”—in English, “god from the machine”—derives from a famous plot device used in ancient Greek and Roman plays. Toward the end of some of these plays, in which the plot involves a seemingly insurmountable difficulty, a god would appear—hence, the “deus”—and use divine power to resolve the difficulty. Often the person portraying the god would fly into the play’s scene, suspended in the air by a crane using ropes and pulleys—hence, the “machina”. Euripides, an ancient Greek playwright, was famous for using this sort of plot device.
Leibniz considers three main options for giving a general explanation of the appearance of causal interaction in the world.
The first is interactionism, which says that things in the world really do cause changes in each other. When we high-five, your hand really does cause changes in the surface of my hand, which eventually causes changes in my mind. As suggested above, Leibniz thought interactionism wasn’t possible.
The second option is occasionalism, which says that things appear to cause changes in each other, but actually they don’t. God is the one who really causes the changes. On the occasion of your hand slapping mine, God directly causes the changes in my hand; and on the occasion of those changes in my hand, God directly causes the changes in my nervous system, and so on, all the way through the causal chain ending with my mind experiencing a stinging sensation. Again, as suggested above, Leibniz thought occasionalism wasn’t true.
The third option is what Leibniz arrives at in the following passage:
Page 77
Being then obliged to admit that it is not possible for the soul or any true substance to receive any influence from without, if it be not by the divine omnipotence, I was led insensibly to an opinion which surprised me but which appears inevitable and which has in truth great advantages and many beauties. It is this: it must then be said that God created the soul, or every other real unity, in the first place in such a way that everything with it comes into existence from its own substance through perfect spontaneity as regards itself and in perfect harmony with objects outside itself.
Leibniz thought that each substance—or, as he says here, each “real unity”—must be causally active, i.e., they can cause real changes in the world. He thought that if a substance doesn’t do anything, it can’t be a real thing at all! So, if substances are causally active but can’t truly cause changes in each other, well, then each substance must be causing only and all the changes that happen to itself! That’s what Leibniz means by saying that “everything with it comes into existence from its own substance through perfect spontaneity as regards itself”.
God also chose to bring into existence only those substances (e.g., me, you, your dog, etc.) that would, of their own internal “programming” (so to speak), cause changes in themselves that would match up perfectly with the changes in every other substance. If you’ve ever been to Chuck E. Cheese and seen their animatronic band, you know that these characters aren’t really playing music interactively together in the usual sense. They can’t really hear each other, and they don’t really adjust their timing to one another. Instead, each band member is pre-programmed to play its part, and each member’s programming is designed to sync up perfectly with the others’. That way, so long as each animatronic band member is switched on at the same time, they’ll all appear to interact, even though they’re each just following their internal programming. That’s kind of like what God did in creating the world, according to Leibniz! God chose to create a world including all and only those substances whose internal “programming” would perfectly match up with each other, in perfect harmony. That’s why Leibniz’s theory is called the pre-established harmony. This isn’t the same story as occasionalism, though, since God isn’t constantly causing everything directly. Instead, God did all the “programming” from the beginning.
What sorts of changes are caused internally? Well, everything. But that also means, perhaps most interestingly, everything that you consciously experience—that is, all your internal sensations or phenomena (i.e., appearances), as Leibniz puts it—are caused internally as well.
Pages 77-78
And that thus our internal feelings (i.e., those within the soul itself […]), being only phenomena consequent upon external objects or true appearances, and like well-ordered dreams, it is necessary that these internal perceptions within the soul itself come to it by its own proper original constitution, i.e., by the representative nature (capable of expressing beings outside itself by relation to its organs), which has been given it at its creation and which constitutes its individual character. This beings it about that each of these substances in its own way and according to a certain point of view, represents exactly the entire universe, and perceptions or impressions of external things reach the soul at the proper point in virtue of its own laws, as if it were in a world apart, and as if there existed nothing but God and itself […] there is also perfect harmony among all these substances, producing the same effects as if they communicated with each other by a transmission of kinds or of qualities, as philosophers generally suppose.
So, when I (seem to) high-five your hand, and you experience that stinging sensation, it’s really you that caused that stinging sensation in yourself. And it’s also really you that caused the preceding visual appearance of my hand swinging toward yours to high-five you. All along, it’s all been you causing these experiences. Of course, because God has created a world of beings (like you and me) whose internal natures are pre-harmonized, each of these beings’ series of life experiences will perfectly correspond to every other being, which is why Leibniz says these are all like “well-ordered dreams”. And also, because of this perfect harmony, we can say that each being’s own internal appearances represent the world of beings around it, even though all those beings are, strictly speaking, causally closed off. When I experience your hand slapping mine, this experience represents you, since you’ve got a corresponding experience of your own hand approaching mine, from your point of view. All this is true, even though every created substance (e.g., you or me) exists, as Leibniz puts it, “as if in a world apart”, since we never actually causally interact.
So, that was all about what goes on in the mind or soul. But how does Leibniz use his pre-established harmony to explain how the mind interacts with the body? Ultimately, the pre-established harmony of everything provides the underlying explanation.
Page 78
Farther, the organized mass, within which is the point of view of the soul, being expressed more nearly by it, finds itself reciprocally ready to act of itself, following the laws of corporeal machines, at the moment when the soul wills it, without either one troubling the laws of the other… it is this mutual relationship, regulated beforehand in every substance of the universe, which produces what we call their inter-communication and alone constitutes the union between the soul and body. And we may understand from this how the soul has its seat in the body by an immediate presence which could not be greater, for it is there as the unit is in the complex of units, which is the multitude.
Now, there’s some controversy about what Leibniz thinks bodies really are. Most scholars think that, at some point in his career, Leibniz came to believe that bodies aren’t really substances at all, but rather are in some sense composed of the phenomena experienced by the only true substances, i.e., minds. But what’s important to see here is just that these “organized masses” (i.e., bodies)—whatever their ultimate nature—are also pre-programmed to change in harmony with the wills of the corresponding minds!
Leibniz emphasizes that his pre-established harmony theory is better than the other two competing theories (interactionism and occasionalism). Why? Because, for one thing, pre-established harmony is possible, whereas the other two, in Leibniz’s view, aren’t even possible. That’s a low bar to clear, you might think. But if there are only three possibilities, and if two of them turn out not to be possible, well, then the third must be true, right?
Page 78
This hypothesis is very possible. For why could not God give to a substance in the beginning a nature or internal force which could produce in it to order (as in a spiritual or formal automaton, but free here since it has reason to its share), all that which should happen to it; that is to say all the appearances or expressions it should have, and that without the aid of any creature? All the more as the nature of the substance necessarily demands and essentially includes a progress or change, without which it would not have power to act. And this nature of the soul, being representative, in a very exact (although more or less distinct) manner, of the universe, the series of representations which the soul will produce for itself will naturally correspond to the series of changes in the universe itself; as, in turn, the body has also been accommodated to the soul, for the encounters where it is conceived as acting without. […] Thus from the moment the possibility of this hypothesis of harmonies is perceived, we perceive also that it is the most reasonable and that it gives a marvelous idea of the harmony of the universe and of the perfection of the works of God.
Let’s pull together some of the threads above and organize Leibniz’s case in favor of pre-established harmony as an argument.
Premise 1: The only ways to explain the appearance of causal interaction between minds and bodies (or, really, between any two created substances) are (a) interactionism, (b) occasionalism, or (c) pre-established harmony. There aren’t any other candidate explanations.
Premise 2: Interactionism is false.
Premise 3: Occasionalism is false.
Conclusion: The only way to explain the appearance of causal interaction is pre-established harmony.
Why think premise 1 is true? The idea is that any explanation you can come up with is ultimately going to boil down to a version of one of those three theories. Is that true? I’ll leave it to you to consider, and we have already seen Leibniz’s arguments for premises 2 and 3, that interactionism and occasionalism are false.
So, the only theory left standing as a possible explanation is Leibniz’s pre-established harmony. Leibniz, of course, can offer additional reasons for the claim that God used pre-established harmony, but here it’s enough for him to show that pre-established harmony is the only game in town.
Clever readers might notice that the conclusion here is really only that pre-established harmony is the only explanation for the appearances of causal interaction. But might it be that there’s just no explanation at all? The argument doesn’t rule that out. However, Leibniz is well-known for believing the principle of sufficient reason, which says that “no fact can be real or existent, no statement true, unless there be a sufficient reason why it is so and not otherwise” (p. 222, The Monadology). And so, since there must be an explanation, and since pre-established harmony is the only explanation, pre-established harmony must be true.
So, Leibniz denies that anything (except God) really has any causal power, really interacts with anything else. Reality appears to be full of causal interactions, but that’s only an appearance. However, Leibniz thinks it’s still totally fine to talk as if things in the world causally interact.
Page 79
The customary ways of speaking can still be retained. For we can say that the substance, the disposition of which explains the changes in others in an intelligible manner (in this respect, that it may be supposed that the others have been in this point adapted to it since the beginning, according to the order of the decrees of God), is the one which must be conceived of as acting upon the others. Also the action of one substance upon another is not the emission or transfer of an entity as is commonly believed, and cannot be understood reasonably except in the way which I have just mentioned.
We can still say that your hand slapped mine, that you caused me to experience a stinging sensation. This is no problem, so long as we understand that, really, it’s all pre-established harmony.
In “A New System of Nature”, Leibniz argues that pre-established harmony is the correct explanation for the appearance of systematic and law-like causal interactions in the world. On this theory, nothing in the world that God created truly directly interacts, even though it looks like it. Instead, all these appearances are caused internally by each of us independently, according to our very natures. And God selected each of us in part because each of our internal natures would match up with every other, so that we’d each individually and actively represent the world in perfect harmony with everyone else.
If you want to read more about Leibniz’s famous pre-established harmony, you can read a number of additional explanations he offered in response to his readers and critics, starting at p. 81 of Duncan’s The Philosophical Works of Leibnitz.
If you want to learn more about Leibniz’s philosophical views in general, take a look at these articles in the Internet Encyclopedia of Philosophy and the Stanford Encyclopedia of Philosophy.
This work has been adapted from “A New System of Nature”, found in The Philosophical Works of Leibnitz, a title found at the Library of Congress. This work is in the public domain. All images were created using Midjourney.
Flattery, Tobias. 2024. “High Fives and Pre-Established Harmony: Gottfried Wilhelm Leibniz’s A New System of Nature.” The Philosophy Teaching Library. Edited by Robert Weston Siscoe, <https://philolibrary.crc.nd.edu/article/pre-established-harmony/>
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.
