Externalism, Self-Knowledge and Transmission of Warrant

Externalism about some mental property, M, is the thesis that whether a person (or other physical being) has M depends, not only on conditions inside the person’s skin, but also on the person’s environment and the way that the person is embedded in that environment. The dependence here is supposed to be conceptual rather than causal; it is the kind of dependence that can be revealed by philosophical theorising. This is an armchair methodology; so, if philosophical theorising yields knowledge, then it is a kind of armchair knowledge. Its status as knowledge does not depend on our conducting any detailed empirical investigation of the world around us. The puzzle for discussion in this paper arises when the possibility of armchair knowledge of an externalist dependence thesis about mental property M is put together with a thesis of first-person authority for that same mental property. For the purposes of generating our puzzle, we do not need to be concerned about a precise formulation of the notion of first-person authority. All that we need to suppose is that we each have a distinctively first-personal way of knowing that we ourselves have property M, when we do have it, without needing to conduct any detailed empirical investigation of the environment and our relation to it. This distinctively first-personal knowledge, self-knowledge, is another kind of armchair knowledge. The puzzle that arises from combining externalism and self-knowledge is clearly visible when we consider the epistemic status of the premises and conclusion of arguments of the following form (Ext): Ext(1) I am thinking that p. Ext(2) If I am thinking that p then E(me). Therefore: Ext(3) E(me). (‘E(x)’ is some statement about x’s environmental embedding.) The occurrence of the particular mental verb ‘think’ in Ext(1) is not vital; we could just as well have ‘I believe that p’. All that is vital is that the mental property of thinking or believing that p should meet two conditions. First, it should be a property that is subject to first-person authority. Second, it should be a property for which an externalist dependence thesis