The centerpiece of Schlick's early epistemology is a deep cleavage between intuitive acquaintance and conceptual knowledge.
Schlick expended considerable effort discussing the differences between intuitive acquaintance and conceptual knowledge, insisting that, even though intuitive images are real, acquaintance with them does not constitute knowledge.
If, on the one hand, the acquaintance or awareness is propositional or conceptual in this way, then while such acts or episodes of awareness seem capable, in principle, of justifying other beliefs, they would surely need to be justified themselves.
In short, the attempt to identify intuition as a form of knowledge is simply a conflation of knowledge with acquaintance, of unelaborated, direct perception or sensation with conceptual knowledge, of kennen with erkennen (Schlick 2009, Sec. 12).
Is the awareness or acquaintance that is the alleged source of noninferential justification propositional or conceptual?
Of course, Klee is far from alone in bearing this "cost," but his semi-abstraction did help open the door for the abstract and conceptual art movements that followed, the merits of which Heidegger remained more skeptical about, as his acquaintance with them was minimal (as Young 2001 shows).
Still, one philosopher's conceptual atom is another's complete mystery, and unless one can convince oneself that one understands what acquaintance is, one will not be able to understand views that invoke it.
This thesis directly confronts the idea, held by a number of philosophers, that acquaintance with intuitive contents is, indeed, a species of knowledge which is more direct and immediate than conceptual knowledge.
Thus, the conceptual categories exist only potentially, but not actually, in extra-mental reality; it is possible for the intellect, upon acquaintance with one of the actual categories in extra-mental reality, to form the concept of the corresponding conceptual category (on Auriol's ideas on the category most broadly, see Amerini 2014).
Moore is well aware that this analysis of the nature of a proposition leads to some version of what could be called "conceptual realism," according to which that what is "really" real are concepts because they are the ultimate objects of acquaintance.
