This paper will be concerned with the role acquaintance plays in contemporary theories of introspection. Traditionally, the relation of acquaintance has been conceived in analytic epistemology and philosophy of mind as being only epistemically relevant inasmuch as it causes, or enables, or justifies a peculiar kind of propositional knowledge, i.e., knowledge by acquaintance. However, in recent years a novel account of the role of acquaintance in our introspective knowledge has been offered. According to this novel constitutive approach, acquaintance is, in (...) itself, a sui generis—i.e., non-propositional—kind of knowledge. As we will suggest, a stalemate between David Chalmers’ account of direct phenomenal concepts—as a prototypical example of a causal view—and Anna Giustina’s account of primitive introspection—as a prototypical example of a constitutive view—is looming in the current controversy between the two families of theories. Towards the end of the essay, we will point to some possible ways for a constitutive theorist to break the stalemate. (shrink)