“Suppose I say I will call the sensation which I now have 'S'. To do this I point inwardly to the sensation.—But 'pointing to the sensation' is not a procedure I go through. Rather, the word 'S' is defined by means of the gesture pointing at the part of the body where the sensation is felt. But this definition does only make sense if the name 'S' gets a use in the language-game other than to name this sensation.”
Wittgenstein's critique of private language: there cannot be a purely private language—words must be publicly checkable (through use, criteria, correction). This undermines Cartesian dualism (private mind) and solipsism (only I know my experiences).
Practically, this means even 'private' sensations (pain, emotion) are known and expressed through public language. This has psychological implications: subjective experience is intersubjective; others can understand my pain through the language-game of pain. This influenced later philosophy of mind and interpersonal psychology.
Commentary
Wittgenstein's critique of private language: there cannot be a purely private language—words must be publicly checkable (through use, criteria, correction). This undermines Cartesian dualism (private mind) and solipsism (only I know my experiences).
Practically, this means even 'private' sensations (pain, emotion) are known and expressed through public language. This has psychological implications: subjective experience is intersubjective; others can understand my pain through the language-game of pain. This influenced later philosophy of mind and interpersonal psychology.