Sven Bernecker

In this paper I argue in favor of the compatibility of semantic externalism with privileged self-knowledge by showing that an argument for incompatibilism from switching scenarios fails. Given the inclusion theory of self-knowledge, the hypothesis according to which I am having twater thoughts while thinking that I have water thoughts simply isn't a (entertainable) possibility. When I am on Earth thinking earthian concepts, I cannot believe that I am thinking that twater is wet for I don't have the concept of twater available; so this concept cannot figure in any of my mental states. Analogously, when I am on Twin Earth, I cannot mistakenly believe that I am entertaining water thoughts. No matter how often I am switched between Earth and Twin Earth, I will never erroneously think that I am having water thoughts while in fact I am having twater thoughts and vice versa. Privileged self-knowledge is therefore immune to skeptical arguments from switching and twinning scenarios.

This paper addresses the question whether introspection plus externalism about mental content warrant an a priori refutation of external-world skepticism and ontological solipsism. The suggestion is that if thought content is partly determined by affairs in the environment and if we can have non-empirical knowledge of our current thought contents, we can, just by reflection, know about the world around us -- we can know that our environment is populated with content-determining entities. After examining this type of transcendental argument and discussing various objections found in the literature, I argue that the notion of privileged self-knowledge underlying this argument presupposes that we can learn, via introspection, that our so-called thoughts are propositional attitudes rather than contentless states. If, however, externalism is correct and thought content consists in the systematic dependency of internal states on relational properties, we cannot know non-empirically whether or not we have propositional attitudes. Self-knowledge (apropositional attitude) is consistent with us lacking the ability to rule out, via introspection, the possibility that we don't have any propositional attitudes. Self-knowledge provides us with knowledge of what is in our minds, but not that we have minds. Hence, the combination of externalism with the doctrine of privileged self-knowledge does not allow for an a priori refutation of skepticism and is therefore unproblematic.

Incompatibilism is the view that privileged knowledge of our own mental states cannot be reconciled with externalism regarding the content of mental states. Davidson has recently developed two arguments that are supposed to disprove incompatibilism and establish the consistency of privileged access and externalism. One argument criticizes incompatibilism for assuming that externalism conflicts with the mind‐body identity theory. Since mental states supervene on neurological events, Davidson argues, they are partly ‘in the head’ and are knowable just by reflection. Another argument rejects incompatibilism by repudiating the object perception model of introspection. Once extemalism is freed from the internalist idea that thoughts take objects which are inner epistemological intermediaries, Davidson maintains, it poses no threat to privileged self‐knowledge. It is argued that neither of these arguments is successful, since both disprove assumptions irrelevant to incompatibilism. Moreover, it is indicated how Davidson would have to go about defending his positive account of privileged self‐knowledge against the principal incompatibilist arguments.

Hilary Putnam has famously argued that “we are brains in a vat” is necessarily false. The argument assumes content externalism (also known as semantic externalism and anti-individualism), that is, the view that the individuation conditions of mental content depend, in part, on external or relational properties of the subject’s environment. Recently content externalism has given rise to the hypothesis of the extended mind, whereby mental states are not only externally individuated but also externally located states. This chapter argues that when content externalism is combined with the extended mind hypothesis it is robbed of its anti-skeptical power. Given the extended mind hypothesis, the supercomputer and the envatted brain can be regarded as aspects of the extended mind of the evil scientist. On this view, the thought contents of the coupled brain–computer–scientist system do not differ from those of a normal human. But without a difference in thought contents Putnam’s anti-skeptical argument crumbles.