Descartes Knew More Than He Thought

Old Renes, Looking Very FrenchYou can only know what is true. For example, everybody knows the statement “If p is true then p is true” is true (just why in a moment). You can believe what is true or what is false. Thus many believe the statement “President Obama has never engaged in demagoguery” which is false (again, just why in a moment).

Rene Descartes famously wondered just what he really knew and what might be mere belief. That is, what is certain and what might be doubted. According to Stanford’s Encyclopedia of Philosophy:

Descartes understands doubt as the contrast of certainty. As my certainty increases, my doubt decreases; conversely, as my doubt increases, my certainty decreases. The requirement that knowledge is to be based in complete, or perfect certainty, amounts to requiring a complete absence of doubt — an indubitability, or inability to undermine one’s conviction. Descartes’ methodic emphasis on doubt, rather than on certainty, marks an epistemological innovation. This so-called ‘method of doubt’ will be discussed below

As nearly everybody who has attended at least one college course has heard, Descartes stripped away every piece of information for which he could express the least doubt. Again, the SEP (quoting Descartes):

I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I too do not exist? No: if I convinced myself of something then I certainly existed. But there is a deceiver of supreme power and cunning who is deliberately and constantly deceiving me. In that case I too undoubtedly exist, if he is deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something. So after considering everything very thoroughly, I must finally conclude that this proposition, I am, I exist, is necessarily true whenever it is put forward by me or conceived in my mind. (Med. 2, AT 7:25)

All will recognize this as part of the (in)famous cogito ergo sum. Although this is too summary, Descartes argued that this was the most fundamental or basic truth. Now, other truths existed or could be deduced from the basic truth, but the cogito (Descartes thought) begins it all.

Of course, it is true that “Because I think I therefore exist,” but in saying that, I (and Descartes) am actually admitting to more knowledge than just this statement. That is, I—and I say “I” because the cogito allows me to doubt “you”—am implicitly arguing that I know more than just that I exist. Can you see it? It is yet another lovely proof that empiricism is false. Empiricism, as Scruton defines it, is the desire that:

(i) All claims to knowledge are based on knowledge of experience: experience is the ‘foundation’ of knowledge.
(ii) Experience can provide such a foundation only if my beliefs about my present experiences are immune to error…
(iii) But my experience does provide a foundation, since the realm of experience is ‘set apart’ from the physical world: it is a realm off ‘privileged access’ where (and I alone) am sovereign…

Now it might appear that the cogito is known by experience, just as we know that the “demagoguery” statement is false from experience. I experience me and from that deduce that I must exist. But that sentence gives the game away—can you see it yet?—for how can I know how to deduce truths from experience? To make it clear: I start with the knowledge of me, but then I must use certain truths of logic to deduce from my observation that I in fact exist. But how did I know those truths of logic, the rules that allow and produce deductions?

I cannot know these truths from experience and there isn’t any way to bootstrap this knowledge to use in the proof of the cogito (and if there isn’t a way for me to do this, there is no way for anybody; there cannot be an infinite regress; the process has to begin somewhere). Just as I cannot know from experience that for any p that “If p is true then p is true” is true. I just know it (and other similar statements) are true.

Therefore, we must come pre-built with these (and other) truths, which is a long way of saying that truth exists and thus these truths must be acknowledged. But where do those pre-built truths come from? Well, the answer is obvious—which is why some desire empiricism.

A bit busy this week with my new gig. I’ll be a little slow answering comments.


  1. Carmen D'oxide

    “But where do those pre-built truths come from?” I would guess that they must come from somewhere outside of “reality,” that is, beyond, above, and superior to the natural universe. If they were part of the natural, then they wouldn’t have ultimate standing. Unlike rules of the game (e.g., the laws of physics), these truths pervade all aspects of the game instead of merely defining specific operations.

  2. Luis Dias

    Pure knowledge. By gods, you are a god, mr Briggs! You just know things!

    I mean, it’s not like you are trying to glue all your knowledge of logic and “pure thought” that you have inherited throughout your entire life in our culture into an hypothetical case study where you know nothing but that you exist.

    IOW, you assume you know these things and then you go on concluding that it is amazing that you do know these things. I’m happy for your happiness on these matters. I am also smugly and annoyingly laughing my backside at the circularity of your reasoning.

  3. Outlier

    Descartes didn’t see The Matrix (belief, no doubt). Descartes might have had dreams, and if he did, he might have wondered like some other philosophers which was the real reality, and he might have wondered if when he himself made an appearance in his own dreams, what did that say about thinking he existed? He got more fame from this statement than it deserves. Was there any skepticism at the time?

  4. Luis Dias

    If they were part of the natural, then they wouldn’t have ultimate standing

    I’m always amazed how easy it is for people to just sprout these absolute statements from their own heads. Of course, it may well be true, that they “wouldn’t have ultimate standing”. One wonders what the hell does that even matter. Will the dying universe a trillion years in the future really care if these matters “still stand”? What the hell does “forever” even mean. All very funny concepts that share the same characteristic here (i.e., that are unknowable by man) being used and abused as if we are talking about common things like rain or sunshine.

    A little more humbleness should be required. It could start off by saying “I promise not to limit the infinite to my prejudices”.

  5. GoneWithTheWind

    There are many innocent people in prison because the law and unethical lawyers (sorry for the redundancy) get to determine what is truth and even what can be uttered. In life outside of the law many truths get trampled by special interest and power. Truth is often difficult to ferret out but just as often truth is intentionally buried over a favored version of “truth”.

  6. Carmen D'oxide

    Luis, a humble man takes his own advice.

  7. JH

    What is the contrapositive of the statement “I think I therefore exist”?

    I don’t exist because I don’t think.


  8. JH

    “I think therefore I exist”? (Haste makes waste!)

  9. JH

    Damnit, I wasn’t thinking!

  10. Eric Anderson


    What does inherited knowledge and culture have to do with with Briggs’ example? I trust you’re not suggesting that knowledge of one’s own existence is a relative cultural projection that might or might not work in another culture. Briggs is talking much more basic than that. Strip away all your relativistic cultural stuff, as well as the learned “knowledge” through life, and what are you left with? That is the question Briggs (and Descartes) is looking at.

  11. Ken

    RE: “But how did I know those truths of logic, the rules that allow and produce deductions? I cannot know these truths from experience and there isn’t any way to bootstrap this knowledge to use in the proof of the cogito (and if there isn’t a way for me to do this, there is no way for anybody; there cannot be an infinite regress; the process has to begin somewhere). …. Therefore, we must come pre-built with these (and other) truths,….”

    BAH HUMBUG – One doesn’t need to look too far or hard to quickly realize that “truths of logic” that at one point seemed so ‘in-built’ are, in fact, VERY HEAVILY determined or influenced by learned knowledge. Maybe not “experience” but learned just the same. This is particularly evident where the ‘in-built’ (or “pre-built”) [so-called] “truths” turned out to be falsehoods:

    The concept of zero we take so much for granted was, in its day, a sophisticated innovation (think about how much obvious facts & truths derive from the concept of zero now…which, in considering, clearly reveal those “pre-built” “truths” are neither “pre-built” or, necessarily, true prior to the invention of zero).

    The Earth-centric perspective of the universe, for example, led to numerous logical, and wrong, conclusions that seemed, then, oh-so-self-evident…

    Matter was believed indivisible below a certain point (“atom” was the word invented to describe this)…

    The “ether” was deduced from similar “logic”….and we know the “ether” as then-accepted does not exist…


    All built on, what would then be considered “pre-built” (‘in-built’) “Truths” that turned out be not just off a bit, but wildly, fantastically, wrong.

  12. hmi

    @Erik Anderson

    “Strip away all your relativistic cultural stuff, as well as the learned “knowledge” through life”

    Shall we include language as one of those cultural things that qualify as learned acquisitions and which will be stripped away?

  13. Matt

    “I think therefore I exist”

    How do you know you were thinking? Maybe you are a figment of my imagination and I was imaginining that you were thinking.


  14. Big Mike

    I know I exist.

    I *know* I know I exist.

  15. Bill S

    You remind me of a beagle following it’s nose.
    No brains. No thought. Just reaction.
    It would be a good thing if you either went away or started to think.

  16. Uncle Mike

    The comments above fail to attain understanding of the essay. If existence was experienced as no more than a endless train of sensory inputs without memory, then could Descartes engage in thinking? What is thinking anyway but the reflection upon past experience via memory?

    What does it mean to “make sense” of experience? First memory is required, but then something else is needed. Briggs calls that something else “logic”, the capacity to deduce from sensory memories “truth” — which may indeed be empirical truth such as “hammer on thumb yields pain” or some other verity.

    Of course, thinking is not limited to philosophers. My dog is pretty clever. She figures stuff out, like how to bury something dead and then dig it up later when it’s ripe. I bet Descartes never did that.

  17. Rich

    You can only know what is true but you can’t know that it’s true. We use the label “truth” to signal our certainty or to discuss “everything that is the case”. But since, in the lives we actually lead, it is always elusive we can only try to persuade each other to believe. Certainty just seems to lead to arguments. Which is strange, considering.

  18. Will

    A great read Dr. Briggs!

    Luis– what part of the argument was circular?

  19. JH

    Will, I know the truths because I am pre-built with them. “I just know it (and other similar statements) are true.” Circular?!

  20. Will

    JH: I kind of see what you’re getting at, but it only seems circular if you won’t separate hard-coded rules from derived rules, and I think thats what Briggs was getting at.

  21. Outlier

    I was too hard on Descartes. His idea of removing doubtful information is the essence of being a skeptic. I’m not thrilled by what he chose as a foundation to build upon. He did better in mathematics. BTW, he must have faced very serious risk for being skeptical in that age when not agreeing with the established dogma was heresy.

    What was not realized at that time was that logic is entirely man-made. There is no empirical foundation for it; it can’t be sensed. In that sense it does not ‘exist’. 🙂 It should not be confused with the physical world, whether that exists or not. And further, at that time logic was confused with language and was without a formal foundation, with the result that so many huge claims are taken as given or obvious.

  22. Luis Dias

    Bill S, good day to you too sir!

    Eric, the problem here is obviously that we are speaking at the vantage point of a culture that believes in concepts like individuality, consciousness, free will, etc.,etc.

    Not that I do not share these beliefs, I just don’t take them to be absolutely true. They can be false beliefs, or perhaps more rigorously, they can be very deceiving, equivocal and ambiguous beliefs that are “merely” tangentially true to what’s “really” going on.

    So, whenever someone comes and says “I know I exist” as an absolute, he is merely confused, ignorant of his own prejudices. Does “knowledge” exist? Why yes, it does, but how could we ever reach this “conclusion” if we strip ourselves of everything but our own existence? We couldn’t, of course. And would the word “I” even mean anything if we are to imagine ourselves alone in the dark? We would hear our thoughts, we would direct them, but would we be able to conclude that such a thing is able to form an “I”? I don’t think so.

    The “I” could well be an illusion. We actually do not know this is the case or not. We may outrageously rebel at the possibility, like mr Briggs does and like all status quo in previous centuries have done when confronted with hard truths, but that does not make such problems “disappear”.

    So yeah, Descartes was all wrong. Outlier claims that logic is “entirely man made”, well of course it is. I have yet to see a bird doing algebra. I have also yet to see a non-nonsensical argument on how “man” isn’t a natural object inside this universe. If you know what I’m getting at.

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