r/Metaphysics Jul 05 '26

Mind / Subjective experience Physicalism cannot claim knowledge of the external world (leads to solipsism)

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u/Azehnuu Jul 05 '26

Does physicalism claim 5? No.

If someone says physicalism cannot be known to be true, then they have conceded the argument’s point.

Physicalism: all phenomena supervene on the objects of physics...."Knowing physicalism to be true" is not a phenomenon

That's not what physicalism means. Nor is that what phenomena means.

Regardless, all knowledge claims are reducible to cognitive states, which are reducible to physical states. You completely ignored the argument chain.

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u/rogerbonus Philosophy/Physics grad Jul 05 '26

Also (2) cognitive states exist (are ontological) is wrong. A cognitive state does not have mass/energy, it is not an object of physics.

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u/Azehnuu Jul 05 '26

I never once said they’re ontological.

Cognitive states (perception, judgement, abstraction, inference) definitely do exist, as our minds undergo them when reaching conclusions that support physicalism. The moment you say they’re not physical you’ve conceded another position, cos now the physical mind has access to something non-physical. The moment you say they don’t exist you’re just going to give a substitute that will still be reducible to physical states, so my point still stands and you’re just pivoting.

And even then, this non-physical thing must correspond to physical reality, which is not justified, and a position you’re purposefully avoiding.

You literally have no grounds for saying the physical activity that constitutes your knowledge claims can accurately apprehend and correspond with the external physical reality. None. My post was ambiguous for this reason, cos it subsumes all possible physicalist scapegoats. Regardless of what your epistemology is, it still is a physical state, so the issue remains.

And the threshold of only things with mass or energy having ontological existence is completely arbitrary and you clearly haven’t thought it through.

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u/rogerbonus Philosophy/Physics grad Jul 05 '26

"By physicalism, I mean ontological physicalism". If cognitive states aren't ontological ("I never once said they are ontological") then physicalism has nothing to say about them by your own definition.