Here is an AI-assisted paraphrase of Descartes' second Meditation. The first Meditation is here.
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The Human Mind:
Why It’s Easier to Know Than the Body
1. Yesterday’s meditation left me drowning in doubt. I can’t forget how much I can doubt, and I can’t see any way to certainty. It’s like I’ve fallen into deep water. I can’t touch the bottom, and I can’t keep myself floating on the surface either.
But I’m going to keep going. I’ll take the same approach I took yesterday. I’ll set aside anything I have even the slightest reason to doubt and treat it as if it were completely false.
And I’ll keep going until one of two things happens. Either I will find something that I can be completely certain about, or I will establish with certainty that nothing is certain at all.
Here’s what is keeping me going. You may have heard of Archimedes—the great ancient Greek mathematician and physicist. He once said that if you gave him a single firm, fixed point to stand on, he could move the entire earth.
(He was talking about levers and leverage. If you have a long enough lever and a fixed fulcrum, you can move any weight. He is often quoted as saying, “Give me a place to stand, and I can move the world.”)
I feel the same way about this project. I don’t need to find a hundred certain things, or even ten. I just need one thing. One single thing I can know with complete certainty. If I can find that, I can build everything else from there.
2. So, let’s do this. I’m going to assume that everything I see is just made up. I’m going to assume that nothing my memory tells me ever actually existed. I’m going to act like I have no senses. I’m going to assume that my body, my shape, the space around me, movement, my location—I’m going to act like all of it is just some fiction my mind has invented.
If so, what’s left? What then can I actually hold onto as true?
Could it be just this one thing: that there is absolutely nothing certain?
3. But wait. Just because I’ve stripped everything away doesn’t mean there’s nothing left. Let me think about this more carefully.
Is there something—anything—that I can’t doubt?
What about God (or some kind of being, whatever we want to call it), who is causing all these thoughts to happen in my mind? Maybe there’s a being out there that is causing all my thinking.
Then again, maybe I am causing my own thoughts. Maybe I don’t need to bring God into it at all.
But if I am causing my own thoughts, then I must exist. Am I at least something?
And here is where I hesitate. I just doubted that I have a body and that I have senses. So, if I were nothing but body and senses, then I wouldn’t exist either. Right?
Hold on. I was just now convinced that there was absolutely nothing in the world—no sky, no earth, no minds, no bodies. Was I therefore convinced that I didn’t exist either?
No. Absolutely not. Because I was the one being convinced of all this. Something was doing the convincing. Something was doing the thinking. And that something was me.
So, even if there is an evil demon, a massively powerful, endlessly cunning demon doing everything he can to deceive me, even he can’t make me nothing. Because as long as I am being deceived, I must be something. You can’t deceive nothing.
Therefore, I come to this conclusion after this careful consideration. It seems impossible to escape:
I am. I exist.
That is to say, “I think, therefore, I am.” [1] This “proposition” (pronunciatum) is necessarily true every single time I think it or say it.
As long as I am thinking, I cannot doubt that I exist.
4. But knowing that I exist isn’t enough. I still don’t know clearly what I am. And I need to be careful here. I’ve established one certain thing: that I exist. But now I don’t want to accidentally smuggle in assumptions about what kind of thing I am. That would contaminate the one piece of solid ground that I’ve found: that I exist.
So, let’s go back to basics. What did I think I was, before I started all this doubting? Then let me apply the same filter I’ve been using throughout. Let’s strip away everything that can be doubted, until only what is completely certain remains.
5. So, what did I think I was when we started all this doubting? A man, obviously. But what is a man?
The traditional answer from the time of the Greek Aristotle (384-22 BCE) is “a rational animal.” But that answer just opens up more questions. What exactly is an animal? What exactly is rational? I’d end up chasing definitions down an endless rabbit hole, which is not what I want to do right now.
Instead let me think about what naturally came to mind when I asked myself what I was—before I started all this philosophical questioning.
First, I thought I had a face, hands, and arms. In fact, I thought I had a whole physical body. Mind you, it’s also what you’d see if you looked at a corpse. That’s what I call my “body.”
Second, I thought I did things. I ate, I walked, I perceived things, I thought. I attributed all of that to my soul.
But what exactly the soul was I never really stopped to think about carefully. If I tried to picture it at all, I imagined something extremely light and airy. Maybe it was like wind, or flame, or some kind of invisible gas spread throughout my body. Vague, in other words.
As for the body, I thought I understood that perfectly well. Here’s how I would have described it back then:
“A body is something that has a definite shape. It takes up space and fills that space so completely that no other body can occupy the same space at the same time. It can be perceived by senses like touch, sight, hearing, taste, smell. And it can be moved, though not by itself. It moves if something external acts on it.”
What a body cannot do—or so I thought—is move itself, perceive things, or think. Those abilities seemed like something else entirely. In fact, I was genuinely puzzled when I encountered living things that seemed to have both body and these other mysterious abilities.
6. But here’s the problem. Remember I was exploring what would happen if there were an extremely powerful, malicious being dedicated entirely to deceiving me. I was asking, “What can I actually claim about myself right now in that light?”
Let’s go through the list. Can I claim that any of those physical attributes I just described are real? My shape, space, movement, senses?
No. None of them. If the evil demon is deceiving me about everything physical, then I can’t claim that any of those things are true about me with certainty. So, let’s set the body aside entirely.
What about the various attributes (characteristics) of my alleged soul? I mentioned nutrition and walking. But if I have no body, I can’t walk and I can’t be nourished. Those go out the window too.
What about perception? What about my seeing, hearing, and feeling? Perception requires a body. And besides, I’ve had plenty of experiences in dreams where I thought I was perceiving things that turned out not to be real at all. So, perception goes too.
But wait. What about thinking?
Here’s where everything changes. Thinking is different from all the others. I cannot doubt that I am thinking right now. Even if the demon is deceiving me, the deception itself requires that I exist as something being deceived. And existing as something being deceived requires thinking.
Thinking is the one thing that is completely inseparable from me.
So here is what I can say with complete certainty: I am. I exist. And I exist precisely as long as I am thinking. If I were to stop thinking entirely, I might cease to exist altogether.
So, what am I? Stripped of everything else, I am one thing and one thing only: a thinking thing.
It is a real thing. It is a truly existing thing. I am “a thinking thing.” [2]
7. But wait. Am I anything more than just a thinking thing? Let me push further and see if I can discover something more.
Could I be my physical body? Could I be the collection of arms, legs, organs, and members?
No. I already imagined that all of that might not exist, and yet I would still know I exist. So, I am not my body. [3]
Could I be something like air, or wind, or flame, or vapor? Could I be some kind of invisible physical substance spread throughout my body?
No. I could imagine that all of those things didn’t exist either, and I would still exist. So, I’m none of those things either.
Now, here’s an interesting wrinkle. Maybe those things that I’m imagining don’t exist are actually more connected to me than I realize. Maybe they’re not as different from me as I think.
But I honestly can’t figure that out right now, so I’m going to set that question aside.
Here’s what I can say. I know I exist. And I’m trying to figure out what kind of thing I am. And importantly, I’ve realized that, no matter what I actually am, it doesn’t depend on any of the physical things I’ve been doubting. My existence as a thinking thing is completely independent of my body. [4]
Now here’s something else important. I might be tempted to use my imagination to figure out what I am. But that would be a mistake. Imagination only works with physical things like images, shapes, and bodies. When I imagine something, I’m always picturing something physical.
But I already know that everything physical might be a dream or an illusion. So, using my imagination to understand my mind would be like trying to see something more clearly by going to sleep and dreaming about it. That’s completely backwards.
The conclusion is this: imagination is useless for understanding the mind. The mind can only be understood by the mind itself. That is, it can only be understood by pure thinking, not by picturing anything.
8. So, I’m a thinking thing. But what exactly does that mean? What is a thinking thing?
A thinking thing is something that:
- Doubts
- Understands
- Conceives ideas
- Affirms things (says yes)
- Denies things (says no)
- Wills—wants things, makes choices
- Refuses—doesn’t want things, rejects choices
- Imagines
- Perceives
That’s what I am. All those activities are forms of thinking. And all of them are happening in me right now.
9. That’s actually quite a lot. Think about it. Right now, I am a being who:
- Doubts almost everything?
- And yet understands and conceives certain things?
- Affirms one thing as true and denies others?
- Wants to know more and doesn’t want to be deceived?
- Imagines things, sometimes even when I’d rather not?
- Perceives things, as if through the senses?
Yes. All of that is me. Right now. In this moment.
And here’s the crucial question. Could any of that be false? Even if I’m dreaming? Even if the evil demon is using every trick in the book to deceive me?
No. Because even if everything that I am perceiving is false, the perceiving itself is real. Even if everything I am imagining is false, the imagining itself is real. Even if I am wrong about what I am doubting, the doubting itself is real.
Think about it this way. Right now, I seem to see light. I seem to hear a noise. I seem to feel heat. Maybe I’m dreaming. Maybe the demon is feeding me false impressions. Fine. Let’s grant all of that.
But this one thing cannot be false: that I seem to see, seem to hear, seem to feel. All of that “seeming,” that experiencing, is real. It’s happening. And that experiencing is itself a form of thinking.
Therefore, even my perceptions, even my imaginations—even if their content is completely false—they are still forms of thinking. And thinking is what I am.
10. I am starting to get a clearer picture of what I am. But I have to be honest about something. Even now, after everything I’ve just worked through, physical things still feel more real and more clearly known to me than my own mind does.
I know. That’s strange. Think about what I’m saying. Think about the things I have just called into doubt—the physical world, my body, external objects. Those things probably still feel more vivid and more “real” to me than the thing I’ve just proven actually exists: my own mind.
The doubtful stuff feels more real than the certain stuff. That seems exactly backwards. And yet I can’t seem to help it.
Here’s why this is happening. My mind keeps wandering back to the physical world. I’ve been programmed my whole life to pay attention to things I can see and touch and imagine. Asking my mind to focus on something invisible and non-physical—like itself—is genuinely difficult.
So, here’s what I’m going to do. Rather than forcing my mind to stay focused on itself right now, I’m going to let it wander for a moment. I’m going to let my mind look at the physical world that it is so comfortable with.
But I’m going to do this strategically. In this way, afterward, when I gently pull my mind back to thinking about itself, it will be more settled and more ready to focus.
Think of it like letting a restless child run around for a bit before asking them to sit still and concentrate.
11. OK. Let’s look at physical things, the kinds of things we normally think we know best. Not physical things in general, but one specific physical thing. Let’s do a little experiment.
Take a piece of wax. Say it just came from a beehive. [5] Say that it’s completely fresh. It still smells like honey and flowers.
You can see its color and shape. It is hard and cold. You can easily pick it up and hold it. Tap it with your finger and it makes a sound.
In other words, it ticks every box. It can be known by every single one of our senses. If anything can be clearly and distinctly known through the senses, it is this piece of wax right in front of us.
Now let’s put it near a fire.
Watch what happens. The taste disappears. The smell evaporates. The color changes. The shape melts away. It gets bigger as it melts. It becomes liquid. It gets hot. You can barely touch it now. And if you tap it? No sound at all.
So, here’s the question. Is this still the same wax?
Of course it is. Nobody would seriously argue otherwise. We all know perfectly well that it is the same wax. It’s just in a different state.
But wait. If it’s the same wax, what exactly did I know about it? Everything I knew through my senses has completely changed. The smell, the taste, the color, the shape, the texture, the sound—it’s all different. And yet the same wax remains.
Think about it. Whatever I knew about the wax, it wasn’t anything my senses told me. Something else is going on here.
12. Now let’s ask, “What exactly did I know about the wax?” Let me think about this carefully.
The wax wasn’t the sweetness, or the smell, or the color, or the shape, or the sound. All of those changed. What I knew was something more basic. There was a thing that was presenting itself to me in one set of forms before the fire and in a different set of forms after. The same thing, different appearances.
But what exactly is that thing? Let me strip away everything that changed and see what’s left.
What remains is something that takes up space, that is flexible, and that can move and change. That’s it. That’s the wax underneath all the appearances.
But here’s where it gets interesting. When I say the wax is “flexible,” what do I mean? Do I mean I can imagine it changing from round to square?
Well, yes. But it can change into an infinite number of shapes, not just those two. And I can’t picture an infinite number of shapes in my imagination. So, my imagination isn’t what’s grasping the wax here.
And what about the space it takes up—its “extension” in space? That changes too. It gets bigger as it melts, bigger still as it boils. The wax can expand in ways I have never even imagined.
So again, my imagination isn’t capturing what the wax really is.
Here’s the conclusion: I cannot understand what the wax is through my imagination at all. Only my mind, my pure thinking, can grasp it. [6]
And here is the really fascinating part. What about the wax that I know through pure thinking? Is it a different wax from the one I see and touch and imagine? No. It is exactly the same wax. It always was. I just didn’t realize that what I was actually knowing all along was not coming through my senses. It was coming through my mind.
When I perceive the wax, I’m not really seeing it or touching it or imagining it. I’m doing something called “intuition” (inspectio). It is a direct mental grasp of what the thing is. And that mental grasp can be fuzzy and confused, as it was before I started thinking carefully, or it can be clear and distinct, as it is now.
13. But here is something that genuinely surprises me about my own mind. Even when I am thinking all of this through carefully, language keeps tripping me up.
Here’s what I mean. We say things like “I see the wax.” Not “I judge the wax to be there” or “my mind perceives the wax.” Just “I see it.” And that casual way of talking makes it sound like sight is what is doing the knowing. Like my eyes are the thing in charge.
But think about this. Say I am sitting by a window, and I look down at people passing in the street below. What do I actually see? Hats. Coats. That’s it. I see hats and coats moving along the street.
And yet I say, “I see people.” Without even thinking about it.
But what if those hats and coats were covering robots? Machines controlled by springs and gears, moving around in human clothing? My eyes couldn’t tell the difference. What I actually see is hats and coats. What I know is that there are people underneath them. And that knowing—that judgment—isn’t coming from my eyes at all. It’s coming from my mind.
So, when I say, “I see the wax,” I’m doing the same thing. What my eyes actually give me is a set of colors and shapes. What I know is that there is a piece of wax in front of me. And that knowing is a judgment of the mind, not a report from the senses.
Language hides this from us. But the mind is doing far more work than we give it credit for.
14. But I shouldn’t get too distracted by the way ordinary language misleads us. Someone who is seriously pursuing knowledge shouldn’t need to keep tripping over the way everyday people talk. Let’s get back to the main point.
Here’s the real question. Did I know the wax better when I first encountered it, when I was smelling it, touching it, and seeing it with my own eyes? Or do I know it better now, after thinking carefully about what it actually is and how it can be known?
That’s not even a close call.
When I first perceived the wax, what did I actually have? A set of sensory impressions. I had smell, color, texture, sound.
But honestly? Any animal could have that. A dog can smell the wax. A cat can feel its texture. There’s nothing distinctly human about perceiving the wax through the senses.
But when I strip away all those surface appearances, I realize something different is going on. When I mentally undress the wax, so to speak, and look at what it actually is underneath, I get to real insight. I might still make mistakes in my judgment. But one thing is certain: this kind of knowing, this grasping of what the wax really is beneath its appearances, requires a human mind. An animal can’t do this. A machine can’t do this. [7]
15. Now, let me turn this whole argument back on myself. Remember, I have not allowed that I am anything other than a mind right now. Accordingly, what can I say about my own mind?
I have just spent all this time figuring out that I know the wax better through my mind than through my senses. But if that’s true, then I must know my own mind even better than I know the wax.
Think about it this way. Say I decide that the wax exists because I see it. Well, it’s at least possible that what I’m seeing isn’t really wax. Maybe my eyes are deceiving me. Maybe I don’t even have eyes.
But here’s what’s not possible. It’s not possible that I don’t exist while I’m seeing the wax (or even just thinking that I’m seeing it). The seeing (or the thinking that I’m-seeing) proves I exist. Every time.
And it’s not just sight. If I determine that the wax exists because I touch it, I exist. If my imagination convinces me the wax is there, I exist. Whatever “faculty” I use or reason I give that leads me to believe anything about the wax, the same reasoning proves that I exist. Every single time.
And what is true of the wax is true of every external thing I perceive.
Here’s something worth pausing on. The more faculties I brought to bear on the wax, the more clearly I knew it. These were faculties like sight, touch, imagination, and reasoning. But every one of those faculties derived from my mind. Every time I knew the wax more clearly, my mind was simultaneously revealing itself as the thing doing the knowing.
This fact means that my mind must actually be more clearly known than the wax. And on top of that, the mind has additional ways of knowing itself that have nothing to do with bodies at all. [8]
In the end, what the body contributes to our knowledge of the mind is barely worth mentioning.
16. And just like that, I’ve arrived exactly where I wanted to be.
Here’s what the wax experiment has shown me. Physical things like bodies are not actually known through the senses or through imagination. They are known through the intellect alone. Through pure thinking. We don’t know the wax because we see it or touch it. We know it because we understand it.
And if that is true of physical things, then it follows immediately that my own mind—the thing that does the understanding itself—must be the most clearly and easily known thing of all. It is more clearly known than any physical object. It is more clearly known than the wax. More clearly known than anything.
But I’m not going to rush past this point. I have just overturned something I have believed my whole life: that the physical world is the most real and most clearly known thing there is. It is such a deeply ingrained habit of thought. It won’t just disappear because I have proven it wrong.
So, I’m going to sit here for a while. I’m going to let this new understanding sink in. I’m going to keep thinking about it until it becomes as natural and automatic as the old assumption used to be.
The mind is what knows. And what it knows with absolute certainty is that it exists.
[1] Descartes coined this phrase earlier in his Discourse on Method (1637), but he does not actually use it here in the Meditations. In Latin, it is cogito ergo sum.
I personally agree with the German philosopher Georg Christoph Lichtenberg (1742-99), who argued that Descartes’ argument only implied that “thinking” was happening, not that I was thinking. The concept of a unified “I” requires much further argument.
[2] Descartes uses several Latin terms in this section: mens (mind), animus (soul). These terms are sometimes also translated as understanding or reason. Descartes is not yet sure which term is exactly right. But whatever we call it, his answer is the same: I am a “thinking thing.”
The Latin for “thinking thing” or “thinking substance” is res cogitans. It is one of his most important technical terms. He pairs it with res extensa or “extended thing.” He uses that term to refer to everything physical that takes up space.
The distinction between these two kinds of substance is the foundation of what philosophers call “Cartesian Dualism.” This is the view that mind and matter are two completely different kinds of thing. This idea has been debated by philosophers ever since.
[3] The philosopher Gilbert Ryle famously attacked this conclusion in his book The Concept of Mind (1949). He called Descartes’s picture of the mind a “ghost in the machine.”
Ryle argued that Descartes’s argument was like being shown all the buildings, faculty, and students at a university and then asking, “Where’s the university?” For Ryle, mind wasn’t a separate thing that inhabits the body. It was just what we call the body doing certain things.
[4] The conclusion that the mind is a completely separate substance from the body was famously challenged by Princess Elisabeth of Bohemia (1618-1680), one of Descartes’s most brilliant correspondents. In letters to Descartes, she pressed him on a problem he never fully solved: if mind and body are completely separate substances, how do they interact? When I decide to move my arm, how does an immaterial mind cause a physical arm to rise? This is called the mind-body interaction problem, and philosophers are still debating it today.
[5] If you have never had any experience with wax, you might do a quick search to get a little background.
[6] Descartes uses the Latin mens (mind) and French entendement (understanding) here. Both of them can mean mind or understanding. This is the faculty of pure rational thinking, distinct from imagination or the senses.
[7] Descartes mentions “common sense” (sensus communis). He doesn’t mean common sense in the way we think of it. He means our mental ability to combine and integrate all our different sense impressions into a single unified experience.
[8] Examples might include pure reasoning, self-reflection, or introspection.
