"I think therefore I am" is a much disputed "proof". As an argument, it presupposes many posits.

Being more cautious, one might make the claim, "I only know what I feel." Is this an ontologically closed statement?

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    Attachment of the "I" is one of the most common objections to cogito, and you variant still has it. I am not sure what "ontologically closed statement" means, but if it is supposed to be something like "basic self-evident truth" there is no such thing, as multiple failed attempts over the centuries show. The root of the problem is that to express such a truth one has to use acquired meanings (of "I", "think", "feel", "know", etc.), and anything they can express is derived, not basic. – Conifold May 21 '17 at 22:25
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    @Conifold the major difference, and hence my question, is that because the statement has two I's each refers to the other and thereby ovoids the objection since the I becomes a circular definition - hence the closedness of the question. – martin May 21 '17 at 22:42
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    Circular "definitions" are not definitions, and you still use "I" as something referred to, so this does not avoid the objection (ego cogito ergo sum was used with "I" on both sides too). But as I said the dilemma is not specific to "I", whatever is expressed has to be meaningful, and hence not "ontologically closed", or otherwise it is gibberish. – Conifold May 21 '17 at 22:53
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    @Conifold yes, it was rather lazy of me use circular definition to describe it - what i really meant was the subjects effectively cancel - leaving "I (subject) know what I (subject) feel" or really "I know what I know" (gibberish - as you say - or is it?) Can know be substituted for feel ontologically? – martin May 21 '17 at 23:04
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    Again, I am not sure what "substituted ontologically" means, but none of this can be done purely "ontologically", I think. There is an obvious mediation of language and reference at every step. To use the "I" twice in the same "sense" you need some reference-fixing device. But even subtract "I" and make it impersonal "feeling implies existing", and you are still trapped by semantics of "feeling", "implies" and "existing". – Conifold May 21 '17 at 23:21

'I think only what I feel' is the posit that Hume took. He took sense-impressions as basic and claimed we know of nothing else.

It is also at the root of the positivistic philosophy where 'I know only what I can measure'.

This had it successes. It was at the root of Ernst Machs philosophy of empiriocriticism which he had written about in his book on mechanics.

Poincare went from here to give an operational definition of simultaniety which Einstein used to come up with Special Relativity. It also guided Heisenberg in his own discoveries about QM.

Einstein himself was a famous adherent of the Machian philosophy. But this was as a young man. When he was in his forties, he repudiated it. At a physics colloquium given by Heisenberg at the University of Berlin in 1926, Einstein told the young Heisenberg who was then still a disciple of Ernst Mach:

Possibly I did use this reasoning ... but it is nonsense all the same ... on principle it is quite wrong to try founding a theory on observable quantities alone. In reality, the very opposite happens. It is the theory which decides what we can observe.

Thus, on Einsteins account, the positivistic philosophy in physics is not ontologically closed.

Likewise, Kant showed that in the human sciences that 'I know only what I can feel/know' was wrong, and the far more innocuous statement, 'I am therefore I can feel/know', a statement that most people would not give a second thought to, was truer.

notes: Shimon Malin, Nature Loves to Hide, Quantum Physics and Reality, A Western Perspective.


What do you mean by "know" and "feel"? I'm sure you've happily used the word " know" in places where you weren't talking about things you were feeling directly. Do you doubt that your friend's feet are sore after a marathon, just because you can't feel their pain?

It kind of sounds like the idea of sense-data to me that was popular around Russell's time. Like " I can't be sure that I am really looking at a football at the moment, but I can be sure that I am perceiving the sense data which looks like one" (like seeing these various colours in my visual field). Thus I should, to be correct, in future, say "I see the sense data of a car" instead of "I see a car". To me, it's just a useless change in notation, where the phrase " I see the sense data appearing to be X" will take on the role of " I see X".

  • I don't doubt my friend's feet are sore, because I trust they are not lying to me. But equally, I do not know they are sore - I believe they are sore because I believe they are telling me the truth. But I cannot disbelieve what I feel because I feel it. However, I can disbelieve what I think (believe) because this is secondary to feeling. – martin May 21 '17 at 22:53
  • I guess I might be thinking more along the lines of the idea that using the term "knowledge" is only sensible when you can at least be wrong in principle. If you can't be wrong logically, then you can't really be right about anything either, it's more of a senseless tautology. So I am happy to say "I know Donald Trump is president in the U.S." because in principle it's up for debate. Having a pain is not doubtable in principle, so it's not really meaningful knowledge either is it? – Franz May 21 '17 at 23:36

I think, therefore I am is a valid expression within our rational subjectivity. I think suggests a process, and processes can only be performed by entities, therefore if a process exists, then a processor entity (which is me) exists: then, I exist.

But that is absolutely subjective, and even circular: if I exist and I process, ergo I think.

Nevertheless, it is a valid philosophical axiom: philosophy -and science- are based on rationally-subjective premises as this. Kant tried to make a line between the knowledge we come with, and the knowledge we build over the former one, but I personally think he contradicts himself on his books (and that means he was evolving, that's why he is a great lecture). For me, there is no a-priori knowledge, except our instincts.

For example, temperature is a feeling, and it is very difficult to define physically. The first law of thermodynamics is devoted only to have an objective agreement of what temperature is at a physical level. Temperature is not a property of atomic-level entities, but moreover a feeling on the skin. Nevertheless, it is a fundamental part of the current scientific set of thermodynamical knowledge. That is an example of how philosophy and science are highly dependent on our feelings, just like cogito ergo sum.

Your statement is similar, but personally I prefer it, due to it implies less things. Anyway, it keeps being rationally subjective.

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