P1: I exist (perhaps from the cogito, or just some intuition) as a human being

P2: Human beings must respirate to exist

C1: I am respirating

Surely C1 is synthetic? Or, at least, something that we should not know a priori/by definition. But we clearly do know it a priori, from the concept of human beings?

If it were analytic, it would be necessarily true. But not all humans breathe.

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    How are you getting that "I" from cogito, or "some intuition", is a human being "defined" to require respiration? Do a priori intuitions read physiology textbooks?
    – Conifold
    Commented May 22, 2023 at 19:39
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    Are you aware that the analytic-synthetic divide has criticisms?
    – J D
    Commented May 22, 2023 at 19:42
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    I don't see why any of your propositions are a priori. That I exist is only conditionally knowable given that my existence is a prerequisite for my being able to think about my existence. It is more anthropic than a priori. All kinds of things are necessary for human beings to exist. It is necessary for acetylcholine to be present in my nervous system or I would not be able to think or even live, but knowledge of this fact is not a priori.
    – Bumble
    Commented May 23, 2023 at 4:35
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    P2 is definitely not a priori. Not all definitions are a priori. "A triangle has 3 summits" is a priori, propositions you can logically infer from it are too ("the sum of all angles in a triangle is 180 deg", etc). But the concept of human is not, you need to have met a bunch of humans to come up with a definition of the species a posteriori.
    – armand
    Commented May 23, 2023 at 6:25
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    P1: "I exist" is an intuition and clearly not a priori. "Myself" cannot be independent of "my own" experience. Commented May 23, 2023 at 7:49

1 Answer 1


The apriority/experience distinction is not the most well-framed thing in the philosophical world. Your example seems like it could be characterized as introspective, but:

On a narrow account, “experience” refers to sense experience, that is, to experiences that come from the use of our five senses: sight, touch, hearing, smell, and taste. However, this narrow account implies that justification based on introspection, proprioception (our kinesthetic sense of the position and movements of our body), memory, and testimony are kinds of a priori justification. And if we had different senses, like those of bats (echolocation) and duck-billed platypuses (electrolocation), experiences based on those senses would provide a priori, not empirical, justification on this account which takes a priori justification to be independent of experiences based on the senses we have.

Given these considerations, perhaps “experience” should be taken to mean “sense experience of any sort, introspection, proprioception, memory, and testimony”. This sounds like a hodgepodge of various sources of justification but perhaps what unites them is that, leaving aside memory and testimony, these sources provide us with information either about the physical world or our inner world, either the outer world through perception or the inner world of what we are feeling or thinking, or information about our bodies, through introspection and proprioception. [emphasis added]

But so unless there is something useful about distinguishing pure apriority from introspection, one wonders why knowledge of our own bodily states isn't a priori. The above-quoted article goes on to mention that independence-from-experience is often qualified so as to allow that some of the concepts and proof structures we use a priori to nevertheless be read off experience to a substantial extent. So why make the distinction at all, rather than just differentiate kinds of experiences?

But not all is lost: some philosophers do have a non-superficial sense(!) of apriority. Kant asserts that we have passive, active, and interactive states of consciousness, and experience-by-itself (or sensation, anyway) is passive whereas pure understanding and reason are strongly proactive. So even if we discarded the words "a priori" and "a posteriori," we would still have the apparently real difference between passive and active consciousness in play.& Typically, we have some internal control over our own breathing, which control can be used to facilitate mystical or emotional meditation; and meditation itself can go on to supplement contemplation of arcane geometries with a hint of apriority to their base character (the origin of the shapes used in religious architecture and other symbolism).

What of knowledge-of-breathing as analytical? Per Kripke, it is often thought that "analytical a posteriori" is a genuine kind of knowledge, and the stock example of water being H20 is held to be a necessary truth. As a conditional, it might be, "If anything is water, that thing is H20." So would, "If I'm alive, I'm breathing," be comparably analytical and yet a posteriori? (Note that we assume that existing and living are more or less the same in this context.) Actually, if the flow of oxygen is as essential to human life as having oxygen particles is essential to something's being water, then it does seem as if knowledge-of-breathing might be characterized as analytical yet a posteriori.

&Since there are action-based theories of perception, equating apriority with activity and sensation with passivity could be a non-starter, however, unless the role of action in perception (supposing such a role) goes more towards establishing perception as an interactive combination of a priori concepts and a posteriori sensations. For some generally related issues, see also the SEP articles on:

  1. Bodily awareness.
  2. Embodied cognition.
  3. Action and the logic thereof.
  4. Practical reason and the structure of action.

Or so one might even style knowledge-of-breathing as (potentially) occupying a vague zone between strict apriority and strict experience.

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    That's very helpful. The question I would think about to work out an answer is - what hangs on the answer? I mean, what are the consequences of deciding one way or the other. But I wouldn't rule out the answers that the question is undecideable, or that it depends how you look at it.
    – Ludwig V
    Commented May 23, 2023 at 7:36
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    @KristianBerry it’s interesting to link will and necessity; I find will possibly explaining much of mathematics. But that never seems to be a rock philosophers look under. I also currently hold onto a very strong idea of free will (that’s not that rare at least, it survives in idealism as one possible refuge), largely because I see it as a viable alternative to a mathematical capacity to reason about abstract objects,
    – J Kusin
    Commented May 23, 2023 at 15:14
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    @Kristian Berry I'm afraid I have great difficulty in responding to what you say, because I don't understand the philosophical concept of the will, or indeed of free will. I'm particularly puzzled by the idea of free will as a source of information. I can offer two observations. I'm not sure you will find them helpful. You will recognize Wittgenstein, I'm sure.
    – Ludwig V
    Commented May 23, 2023 at 15:33
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    @JKusin yes, I have trouble believing in an ante rem multiverse of mathematical objects, but I have less trouble believing in a sort of in re multiverse inside each of us (maybe different 'verses for different agents, even). By conflating cardinality with quantification with existence, I then try to see the expanse of large cardinals as somehow encoded into mere existence in general rather than a separate domain of existence. Insofar as existence and reference might be equatable, I then think of "the will to refer," and again large cardinals are "parts of" this will, maybe. Commented May 23, 2023 at 15:34
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    First, I think that the status of analytic (grammatical) or synthetic (contingent or empirical) belongs to the use of a sentence as much as the sentence or proposition. Second observation, I don't think we have the power to survey "always and everywhere"; that pronouncement is a decision about a rule and means that we will always apply it in the same way (which is determined by human agreement).
    – Ludwig V
    Commented May 23, 2023 at 15:35

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