for Frege the privacy of the inner realm consists both in the fact that nobody has anyone’s presentation but her own, and that nobody truly knows anybody’s presentation but her own. Wittgenstein rejects the second claim, but not the first; if anything, he holds to the first in an even stronger form, maintaining, for example, that the affirmations “I am in pain” and “She is in pain” differ from one another not only in epistemic status but even in logical form. Hence the boundary between the inner and outer realms is not entirely erased; but it is blurred, in that the public character of the outer and third realms is extended into the inner realm as well; as Wittgenstein frequently insists: nothing is hidden. (Of course, each of these three realms is public in a somewhat different way, which prevents the boundaries from simply being effaced.)
An action is neither a purely inner-realm item (an “act of volition,” say) nor a purely outer-realm like a bare physical movement; nor is it is simply a conjunction of the two, linked by causation alone. Instead, since the identity of the inner-realm item conceptually depends on its issuing in the outer-realm item, while the outer-realm item in turn is something that is conceptually guaranteed to be evidence (albeit defeasibly so) for the inner-realm item, the inner and outer sides of the action are “internally related” in a single organic unity that straddles the inner-outer boundary. Moreover, insofar as it is logical relations – third-realm items – that connect the inner and outer, all three realms enter into the constitution of action.
Austrians often distinguish between preferences in the praxeological sense and preferences in the psychological sense, where the former are essentially embodied in action while the latter exist whether or not they are acted on. (The Rothbardian rejection of indifference curves, for example, is based on the claim that we are never indifferent between A and B at the moment of choosing A, not that we may not be indifferent between A and B prior to the choice; indifference can exist in the psychological sphere but it can never be expressed in action.) But given Wittgenstein’s solution to the problem of thymological opacity, it’s doubtful that a preference that never receives expression in action can count as a preference at all. Hence so-called “psychological” preferences may require
R. T. Long – Wittgenstein, Praxeology, and Frege’s Three Realms – p. 15