 We said above that what distinguishes the classical, Russellian notion of acquaintance is, minimally, that (i) it is a non-intentional form of awareness: acquaintance with something does not consist in forming any judgment or thought about it, or applying any concepts to it; and (ii) it is real relation requiring the existence of its relata; one cannot be acquainted with some thing, property or fact that does not exist. Let us use the label “acquaintance theory” broadly to stand for any view, in the philosophy of mind or epistemology, in which acquaintance so understood plays a central role. There has been a resurgence of interest in acquaintance theory in the last 25 years or so. Contemporary proponents include BonJour (2001, 2003), Chalmers (2010), Fales (1996), Fumerton (1995, 2001, 2016), Gertler (2001, 2011, 2012), Hasan (2011, 2013), McGrew (1995, 1999), Moser (1989), Stoutenburg (forthcoming), and Taylor (2013). As we shall see, some of these philosophers depart from Russell in significant ways. However, like him, they are all committed to the existence and philosophical significance of a direct, nonjudgmental form of awareness (indeed, many of them call it “acquaintance”) and this warrants treating them all as “acquaintance theorists.” Most of them also explicitly endorse classical foundationalism: like Russell, they hold that all knowledge or justified belief ultimately depends on a foundation of knowledge or justified belief acquired by acquaintance. There are consistent ways to accept acquaintance theory without accepting classical foundationalism. For example, some might agree that we do have some knowledge by acquaintance and appeal to such knowledge in the dualism debate in the philosophy of mind (see the entry on  qualia: the knowledge argument),  without endorsing the claim that all knowledge or justified belief must depend, ultimately, on acquaintance. However, unless otherwise indicated, we use “acquaintance theory” and “classical foundationalism” interchangeably.