I'm working off of Kant's conception of analytic/synthetic and a prior/a posteriori judgements.

The definition of "thoughts" does not subsume their existence. That is, it is logically possible to talk about thoughts in a world where humans are not around to think them. Therefore, "thoughts exist" is not true by the definition of what a "thought" is, and hence not analytic, but rather synthetic.

However, the fact that I am here right now having thoughts means that their existence is necessarily true. I do not need to go outside and look at the sky to confirm this, nor go to the library and read a book to confirm this. The fact that I had a thought necessitates their existence.

  • 2
    No. Feeling pain also does not require looking, at the sky or elsewhere, and you are not having thoughts in dreamless sleep or when you are dead, so having them isn't necessary. Both observations are empirical, i.e. synthetic a posteriori in Kant's terms, like any introspection. That having thoughts implies their existence may well be an analytic a priori conditional, but the fact itself of having thoughts (the premise) isn't a priori, analytic or synthetic.
    – Conifold
    Commented Jul 22, 2020 at 4:03
  • 1. There are no a priori statements, a statement already implies a rational (illusory) judgement (Transcendental Dialectic). A priori refers to a type of knowledge that is necessary for experience. 2. We can only speculate about the synthetic quality of statements.
    – RodolfoAP
    Commented Jun 28, 2023 at 19:36

3 Answers 3


Here's (at least some of) what Kant says about this issue, in the Transcendental Dialectic:

It must, however, appear extraordinary at first sight that the condition under which I think, and which is consequently a property of my subject, should be held to be likewise valid for every existence which thinks, and that we can presume to base upon a seemingly empirical proposition a judgement which is apodeictic and universal, to wit, that everything which thinks is constituted as the voice of my consciousness declares it to be, that is, as a self-conscious being. The cause of this belief is to be found in the fact that we necessarily attribute to things a priori all the properties which constitute conditions under which alone we can cogitate them. Now I cannot obtain the least representation of a thinking being by means of external experience, but solely through self-consciousness. Such objects are consequently nothing more than the transference of this consciousness of mine to other things which can only thus be represented as thinking beings. The proposition, "I think," is, in the present case, understood in a problematical sense, not in so far as it contains a perception of an existence (like the Cartesian "Cogito, ergo sum"), but in regard to its mere possibility—for the purpose of discovering what properties may be inferred from so simple a proposition and predicated of the subject of it.

If at the foundation of our pure rational cognition of thinking beings there lay more than the mere Cogito—if we could likewise call in aid observations on the play of our thoughts, and the thence derived natural laws of the thinking self, there would arise an empirical psychology which would be a kind of physiology of the internal sense and might possibly be capable of explaining the phenomena of that sense.

One might argue that, "Time exists," is tantamount to, "I exist," and that this "I" is thinking, insofar as thinking is conflated with the action of the internal sense; but so on the technicalities of Kantspeak, the internal sense is not the faculty of thought (because of the dynamical distinction between intuition and discursion), and so intuition of my thoughts (intuition of my very faculty of discursion) might seem as a priori as time or as empirical as the objects of time. I suspect that this matter is a moment of potential inconsistency in Kant's theory, or consistency at a very high, and not very clearly known, price.

EDIT: Consider these statements:

  1. The faculty of intuition is different from the faculty of discursion.
  2. The faculties of intuition and discursion exist.

(1) is analytic in that the difference is conceptually displayed; (2) is synthetic because it is an existence claim; but it is perhaps difficult bordering on impossible to say whether (2) is then a priori or empirical or rather something else (a combination of those two characteristics or a separate characteristic altogether). I wish I remembered which of his books it was in, but one neo-Kantian scholar, Allen Wood, defends an empiricist reading of (2) (or of claims akin to (2)), if I remember correctly; I'm not the biggest fan, by any means, of Wood (he's pretty strident betimes), but he's a solid analyst, so worth looking into.


I think that it is true that a 'thoughts exist' is synthetic, but not that it is a priori. Introspection (such as being aware that you are thinking) is a kind of experience.

You are right that, once had, the thought cannot be false - but that isn't the definition of a priori.

  • Thanks for your reply. Isn't an a priori statement one whose truth can be arrived out by logical deduction alone, and not reliant on our contact with the world?
    – Mark
    Commented Jul 21, 2020 at 16:49
  • Yeah but you cannot actually derive this statement ('thoughts exist') by logical deduction (in the way that you can derive 2+2=4 or equivalent). Your knowledge that you exist and are thinking is a type of de se knowledge ('of oneself;'); de se knowledge is very interesting, but it is surely a species of a posteriori knowledge not a priori. Commented Jul 24, 2020 at 8:17
  • "Time necessarily affects the concept of the representations of objects. To affect a priori the act of ob-jectification as such, i.e., the pure act of orientation toward ... means: to bring up against it something on the order of an opposition, "It"—the pure act of ob-jectification—being pure apperception, the ego itself. Time is implicated in the internal possibility of this act of ob-jectification. As pure self-affection, it originally forms finite selfhood in such a way that the self can become self-consciousness." p.195 archive.org/details/kantproblemofmet00heid/page/194/mode/2up Commented Feb 24 at 10:23
  • Sorry, the quote was so long there was no room to introduce it. Just to say above is how Heidegger sees the Kantian origination of thoughts as a priori: a priori apperception. Commented Feb 24 at 13:20

It's analytical or, more properly, not a judgment at all.

In refuting the ontological proof of God, Kant famously says that "existence is not a predicate." One adds nothing to a subject by also stating that it "exists." Like cutting the Gordian knot, that was his way out of a lot of unproductive metaphysical tangles.

However, as I recall, Kant is a bit murky about the status of the self, and I'm not sure what he says about the Cartesian cogito, which might have some bearing on this "purified" version of it.

  • "existence is not a predicate" Of course it is. Of course saying "X exists" and "X does not exist" are both meaningful. To say otherwise means one has forgotten how ordinary language works.
    – user76284
    Commented Jan 16 at 18:20
  • @user76284 This is from Kant's: "A hundred real dollars contain no more than a hundred possible dollars." A599/B627 So if someone dreams up X = a red circular table, then if someone makes an actual red circular table it doesn't change what X is. Commented Feb 24 at 13:44

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