Abstract: Externalism is widely endorsed within contemporary philosophy of mind and language. Despite this, it is far from clear how the externalist thesis should be construed and, indeed, why we should accept it. In this entry I distinguish and examine three central types of externalism: what I call foundational externalism, externalist semantics, and psychological externalism. I suggest that the most plausible version of externalism is not in fact a very radical thesis and does not have any terribly interesting implications for philosophy of mind, whereas the more radical and interesting versions of externalism are quite difficult to support.
Comment: The author sheds light on what the externalist thesis in philosophy of mind actually refers to. More precisely, the author distinguishes between three varieties of externalism, namely, i) foundational externalism, ii) externalist semantics and iii) psychological externalism. After discussing these three varieties of externalism, the author argues that there is a variety of externalism which is non-radical and does not bring about any disastrous conclusion. The first half of the paper can be very useful as introduction on the topic of externalism in philosophy of mind, insofar as lots of the main argument for externalism are addressed and evaluated.