 Symmetrical or self/other parity accounts of self-knowledge treat the processes by which we acquire knowledge of our own minds as essentially the same as the processes by which we acquire knowledge of other people’s minds. A simplistic version of this view is that we know both our own minds and the minds of others only by observing outward behavior. On such a view, introspection strictly speaking is impossible, since the first-person condition on introspection (condition 2 in Section 1.1) cannot be met: There is no distinctive process that generates knowledge of one’s own mind only. Twentieth-century  behaviorist  principles tended to encourage this view, but no prominent treatment of self-knowledge accepts this view in its most extreme and simple form. Advocates of parity accounts sometimes characterize our knowledge of our own minds as arising from “theories” that we apply equally to ourselves and others (as in Nisbett and Ross 1980; Gopnik 1993a, 1993b). Consequently, this approach to self-knowledge is sometimes called the theory theory.