Doubt Everything
René Descartes' Meditations on First Philosophy, Meditation 1

Picture of <b>Wes Siscoe</b><br><small>Assistant Professor of Philosophy, Bowling Green State University</small>
Wes Siscoe
Assistant Professor of Philosophy, Bowling Green State University

Table of Contents

Warm-Up: Is it Possible We are All in the Matrix?

In the science fiction movie The Matrix, Morpheus asks Neo a simple question: Will he take the blue pill or the red pill? If he takes the blue pill, he will go on with his life and forget that he ever met Morpheus. If he takes the red pill, he will learn what the world is really like. As Morpheus says, “All I am offering is the truth, nothing more.”

Neo takes the [Spoiler Alert!] red pill, forever changing his understanding of reality. As it turns out, the world is actually ruled by machines imbued with artificial intelligence. Neo’s actual body is connected to a vast power grid, and his mind has been connected, not to the real world, but to the simulated reality of the Matrix. 

Now this is all pretty far-fetched. From chess-playing computers like Deep Blue to large language models like ChatGPT, computer scientists have made a lot of progress when it comes to artificial intelligence. But we are still far from a place where artificial intelligence could take over and trap us in an entirely simulated world.

At the same time, isn’t it possible that we are in the Matrix? That artificial intelligence has actually already been developed, and that it is now creating the illusion that we are just discovering it? What evidence do you have to rule this out? 

In today’s reading, we will critically examine Descartes’ arguments that reality is not what it appears to be. Even though Descartes wasn’t thinking about the Matrix, he still made the case that we might all be dreaming, or that we might all be deceived by an evil demon. Is there any way that we can rule these things out?

Introduction

René Descartes (1596-1650) was a French mathematician and philosopher and is considered the father of modern philosophy. Coinciding with a period of scientific exploration and discovery in Europe, modern philosophy emphasized the use of reason over a dependence on traditional ways of thinking about the world. Embodying this spirit, Descartes split with many of the medieval and scholastic philosophers that came before him and attempted to build a philosophical system from scratch. In his Meditations on First Philosophy, Descartes begins this project by considering how much we can know about the world around us. 

Descartes splits his meditations up into six parts. In this first meditation, which will be the topic of this reading, he begins by considering which of our beliefs we should be certain about and which we have some reason to doubt. If you’re interested, the full text of all six of Descartes’ Meditations can be found here.

Key Concepts

Cartesian Method of DoubtA 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

A Priori Knowledge – Knowledge that can be gained without having any particular concrete experiences. Such knowledge is typically gained by rational insight or intuition

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

Philosophical Skepticism – The position that we do not know many things that we ordinarily take ourselves to know

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

The Method of Doubt

Descartes begins his investigation by explaining the project he is embarking on and laying out the method he will use to reach his conclusions.

Meditation 1, Paragraphs 1-2

Several years have now elapsed since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation, if I desired to establish a firm and abiding superstructure in the sciences. But as this enterprise appeared to me to be one of great magnitude, I waited until I had attained an age so mature as to leave me no hope that at any stage of life more advanced I should be better able to execute my design.

But, to this end, it will not be necessary for me to show that the whole of [my former opinions] are false—a point, perhaps, which I shall never reach; but as even now my reason convinces me that I ought not the less carefully to withhold belief from what is not entirely certain and indubitable, than from what is manifestly false, it will be sufficient to justify the rejection of the whole if I shall find in each some ground for doubt. Nor for this purpose will it be necessary even to deal with each belief individually, which would be truly an endless labor; but, as the removal from below of the foundation necessarily involves the downfall of the whole edifice, I will at once approach the criticism of the principles on which all my former beliefs rested.

In this passage, Descartes explains that he wants to establish a firm foundation for the sciences. Descartes disagreed with many of the scientists that came before him, particularly in how they were inspired by certain Aristotelian philosophy, and so his project was to create a basis for science that was not vulnerable to such errors. In order to do this, Descartes employs the Cartesian Method of Doubt. Following this method, Descartes doubts all of his beliefs that there is a chance he could be wrong about, even if that chance seems very remote and far-fetched.

Video

Check out this video to hear the Cartesian Method of Doubt explained by a philosophy professor:

Can I Trust My Senses?

Having laid out his project, Descartes begins by applying his method. As he says in the previous passage, he does not plan on considering all his beliefs one-by-one. Instead, he focuses on the sources of his previous beliefs, allowing him to consider a whole category of his beliefs at the same time. The first source that Descartes examines are his senses. Is there anything he has learned through his sight, touch, taste, or smell which he can be certain about?

Meditation 1, Paragraphs 3-4

All that I have, up to this moment, accepted as possessed of the highest truth and certainty, I received either from or through the senses. I observed, however, that these sometimes misled us; and it is the part of prudence not to place absolute confidence in that by which we have even once been deceived.

But it may be said, perhaps, that, although the senses occasionally mislead us respecting minute objects, and such as are so far removed from us as to be beyond the reach of close observation, there are yet many other of their informations (presentations), of the truth of which it is manifestly impossible to doubt; as for example, that I am in this place, seated by the fire, clothed in a winter dressing gown, that I hold in my hands this piece of paper, with other intimations of the same nature. But how could I deny that I possess these hands and this body, and withal escape being classed with persons in a state of insanity, whose brains are so disordered and clouded by dark bilious vapors as to cause them pertinaciously to assert that they are monarchs when they are in the greatest poverty; or clothed [in gold] and purple when destitute of any covering; or that their head is made of clay, their body of glass, or that they are gourds? I should certainly be not less insane than they, were I to regulate my procedure according to examples so extravagant.

Do It Yourself!

When Have Your Senses Deceived You?
Descartes points out that there are occasions where his senses have deceived him. We have all experienced how a stick looks bent when it is half underwater, and how the road ahead can appear wet on a hot summer day. If we are following the Cartesian Method of Doubt, then because our senses have misled us, then we should kick to the curb all of our beliefs that are supplied by our senses. Can you think of any more examples? What is another way that our senses lead us astray?

Am I Dreaming?

At first, Descartes finds it almost unthinkable that he could doubt his senses. But then he considers the possibility that what he is experiencing isn’t actually produced by his senses at all, but is rather part of some elaborate dream. If this is true, he might not be able to trust his experiences after all…

Meditation 1, Paragraph 5

Though this be true, I must nevertheless here consider that I am a man, and that, consequently, I am in the habit of sleeping, and representing to myself in dreams those same things, or even sometimes others less probable, which the insane think are presented to them in their waking moments. How often have I dreamt that I was in these familiar circumstances, that I was dressed, and occupied this place by the fire, when I was lying undressed in bed? At the present moment, however, I certainly look upon this paper with eyes wide awake; the head which I now move is not asleep; I extend this hand consciously and with express purpose, and I perceive it; the occurrences in sleep are not so distinct as all this. But I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming.

Thought Experiment

Can I Tell When I’m Dreaming?
In this passage, Descartes entertains the possibility that everything he is currently experiencing is a dream. His nightgown, his chair by the fire, all of it. Descartes’ key insight is that, if he cannot tell the difference between dreaming and being awake, then he has some reason to doubt the experiences that seem to come from his senses. So that’s the question. Can you tell when you are awake and when you are dreaming? Are there any obvious indicators that give your dreams away? I have had dreams that were so strange that, right in the middle of them, I became convinced that I was dreaming. So maybe it is possible to tell when we’re dreaming. What do you think? Can you tell the difference between when you’re dreaming and when you’re awake?

Physics, Arithmetic, Geometry, Oh My!

If Descartes is right and we can’t distinguish when we are dreaming from when we are awake, what does this mean for our sensory experiences? Should we doubt everything that we learn from our senses? Another issue is how these reflections apply to different areas of study, subjects like physics, arithmetic, and geometry. Can we trust what we learn about these subject matters?

Meditation 1, Paragraphs 6, 8

Let us suppose, then, that we are dreaming, and that all these particulars—namely, the opening of the eyes, the motion of the head, the forth-putting of the hands—are merely illusions; and even that we really possess neither an entire body nor hands such as we see. Nevertheless it must be admitted at least that the objects which appear to us in sleep are, as it were, painted representations which could not have been formed unless in the likeness of realities; and, therefore, that those general objects, at all events, namely, eyes, a head, hands, and an entire body, are not simply imaginary, but really existent. For, in truth, painters themselves, even when they study to represent sirens and satyrs by forms the most fantastic and extraordinary, cannot bestow upon them natures absolutely new, but can only make a certain medley of the members of different animals; or if they chance to imagine something so novel that nothing at all similar has ever been seen before, and such as is, therefore, purely fictitious and absolutely false, it is at least certain that the colors of which this is composed are real. And on the same principle, although these general objects, viz. [a body], eyes, a head, hands, and the like, be imaginary, we are nevertheless absolutely necessitated to admit the reality at least of some other objects still more simple and universal than these, of which, just as of certain real colors, all those images of things, whether true and real, or false and fantastic, that are found in our consciousness, are formed.

We will not, therefore, perhaps reason illegitimately if we conclude from this that Physics, Astronomy, Medicine, and all the other sciences that have for their end the consideration of composite objects, are indeed of a doubtful character; but that Arithmetic, Geometry, and the other sciences of the same class, which regard merely the simplest and most general objects, and scarcely inquire whether or not these are really existent, contain somewhat that is certain and indubitable: for whether I am awake or dreaming, it remains true that two and three make five, and that a square has but four sides; nor does it seem possible that truths so apparent can ever fall under a suspicion of falsity [or incertitude].

Connection

A Priori and A Posteriori Knowledge

Even though Descartes concludes that he cannot trust his senses, that doesn’t mean that we have to throw out everything we believe about the world. In particular, he thinks that we can hold onto our a priori knowledge. A Priori Knowledge can be learned just by thinking. Consider Descartes’ example that 2+3=5. This isn’t something we can only learn by experiencing the world. If I know that I have a carton of 2 apples on the counter and 3 in the refrigerator, I do not need to check and see whether I have 5 apples. I know that 2+3 is always equal to 5, and so Descartes thinks that I do not need to doubt that this is true even when I am dreaming and deceived about my sensory experiences. Among the subjects that can be learned a priori, Descartes includes arithmetic and geometry.

A Posteriori Knowledge, on the other hand, is vulnerable to misleading dreams. A posteriori knowledge can only be gained by learning about the real world, and so if our senses lead us astray, this can prevent us from learning what the world is like. Some examples of things that have been discovered a posteriori include the strength of gravity or that water boils at 100° Celsius. These are not truths that we can arrive at only by thinking, and we only learned about them through scientific discoveries about the way the world works. If we’re dreaming though, all bets are off!

An Omnipotent… Evil Demon?

So far, Descartes has entertained a form of Philosophical Skepticism, doubting that he knows many things which we ordinarily take ourselves to know. But philosophical skepticism can come in stronger or weaker forms. Descartes started out by doubting some of the things which he learned via his senses, and then used the dreaming argument to doubt that he knows anything except certain a priori propositions. In this passage, we’ll see that Descartes thinks that there is reason to doubt even 2+3=5 right alongside scientific claims like water boiling at 100° Celsius.

Meditation 1, Paragraphs 9, 12

Nevertheless, the belief that there is a God who is all powerful, and who created me, such as I am, has, for a long time, obtained steady possession of my mind. How, then, do I know that he has not arranged that there should be neither earth, nor sky, nor any extended thing, nor figure, nor magnitude, nor place, providing at the same time, however, for [the rise in me of the perceptions of all these objects, and] the persuasion that these do not exist otherwise than as I perceive them? And further, as I sometimes think that others are in error respecting matters of which they believe themselves to possess a perfect knowledge, how do I know that I am not also deceived each time I add together two and three, or number the sides of a square, or form some judgment still more simple, if more simple indeed can be imagined? But perhaps Deity has not been willing that I should be thus deceived, for he is said to be supremely good.

I will suppose, then, not that Deity, who is sovereignly good and the fountain of truth, but that some malignant demon, who is at once exceedingly potent and deceitful, has employed all his artifice to deceive me; I will suppose that the sky, the air, the earth, colors, figures, sounds, and all external things, are nothing better than the illusions of dreams, by means of which this being has laid snares for my credulity; I will consider myself as without hands, eyes, flesh, blood, or any of the senses, and as falsely believing that I am possessed of these; I will continue resolutely fixed in this belief, and if indeed by this means it be not in my power to arrive at the knowledge of truth, I shall at least do what is in my power, viz., [suspend my judgment], and guard with settled purpose against giving my assent to what is false, and being imposed upon by this deceiver, whatever be his power and artifice. But this undertaking is arduous, and a certain indolence insensibly leads me back to my ordinary course of life; and just as the captive, who, perchance, was enjoying in his dreams an imaginary liberty, when he begins to suspect that it is but a vision, dreads awakening, and conspires with the agreeable illusions that the deception may be prolonged; so I, of my own accord, fall back into the train of my former beliefs, and fear to arouse myself from my slumber, lest the time of laborious wakefulness that would succeed this quiet rest, in place of bringing any light of day, should prove inadequate to dispel the darkness that will arise from the difficulties that have now been raised.

Argument

The Evil Demon

In this passage, Descartes imagines a demon powerful enough to deceive him about everything he believes (there is actually one key belief that he thinks he can be certain about, but we’ll have to save that for his second Meditation!), giving him at least a small reason to doubt all that he thinks is true. If we lay out The Evil Demon Argument using premises and a conclusion, it would look something like this:

Premise 1: It is possible that I could be deceived by a powerful demon about everything I believe

Premise 2: If it is possible that I could be deceived by a powerful demon about everything I believe, then I cannot be certain about anything that I believe

Conclusion: I cannot be certain about anything that I believe

Descartes motivates the first premise by imagining a demon so powerful that it could deceive him at will, creating vast and complex illusions. In this case, the demon might even be capable of deceiving him about basic arithmetic, so strong would the illusions be. But, as we see with the connection drawn by the second premise, if such a demon does exist, then we cannot be certain about anything that we believe. While it might only provide us with a very small reason to doubt that the reality is as we take it to be, that can still provide us with a small reason for not being absolutely certain.

Summary

In Descartes’ First Meditation, we saw that he wanted to establish a certain foundation for his beliefs. In order to do that, he rejected all beliefs that he had at least some reason to doubt. By considering the possibility that he might be dreaming, he came to think that his senses could not be fully trusted, and the possibility of deception by a very powerful evil demon gave him reason to think that even things he thought he knew a priori, like his mathematical beliefs, could be mistaken. In his Second Meditation, Descartes picks up where we left off, considering whether he has any certain beliefs.

Connection

The Brain-in-a-Vat

Are there any other arguments that can give us reason to doubt everything we believe? In our Warm-Up, we considered a world like the one depicted in the Matrix, where the experiences of most people are of a very sophisticated virtual simulation. If we think that this is a possibility that we can’t rule out, then we could create our own version of Descartes’ argument, starting with the premise that it is possible we are being deceived by very sophisticated artificial intelligence.

In fact, many contemporary philosophers use a different thought experiment than Descartes’ Evil Demon. In its place, they discuss whether we can know that we are not a brain in a vat. The example is discussed so often in philosophy, that there is now even an entire book focused on the thought experiment titled The Brain in a Vat! In many cases where this example is used, the imagined brain is kept alive and hooked up to a simulation by a mad scientist, but it could just as easily be controlled by advanced AI, just like we find in the Matrix.

Want to Learn More?

If you’re curious where Descartes’ method of doubt ultimately takes him, pick up the story with his Second Meditation, where he lands on a conclusion of which he can be certain. And for an overview of how contemporary philosophers think about skepticism, see the articles “Contemporary Skepticism” and “The Brain in a Vat Argument” on the Internet Encyclopedia of Philosophy.

Acknowledgements

This work has been adapted from Meditations on First Philosophy, a title from the eCampusOntario Public Domain Core Collection. This work is in the Public Domain. All images were created using Midjourney and are the property of the Philosophy Teaching Library.

Citation

Siscoe, Robert Weston. 2023. “Doubt Everything: Rene Descartes’ Meditations on First Philosophy, Meditation 1.” The Philosophy Teaching Library. Edited by Robert Weston Siscoe, <https://philolibrary.crc.nd.edu/article/doubt-everything/>.

Key Concept

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.

Key Concept

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.

Key Concept

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).

Key Concept

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?’.

Key Concept

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).

Key Concept

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.

Key Concept

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.

Key Concept

‘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.

Key Concept

By ‘science’, Plato means to be talking about all rational disciplines, including mathematics.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

Was it his burly physique, his wide breadth of wisdom, or his remarkable forehead which earned him this nickname?

Key Concept

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.

Key Concept

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.’

Key Concept

Meletus – A poet and citizen of Athens and one of Socrates’ accusers. Amongst other things, Meletus accused Socrates of impiety and corrupting the youth.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

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.

Key Concept

Recollection – The soul existed prior to birth; during this time it learned everything, and hence all learning is only recalling what we already know.