Mind: A Brief Introduction (John R. Searle) / quote 126 of 138
Internalism versus externalism
The view that I have been tacitly assuming throughout this book is a form of internalism. According to internalism, so construed, our intentional contents are entirely a matter of what is inside our heads. Of course they refer to objects and states of affairs in the world. That is what intentionality is for—to relate us to the world by representing its various features. The content that enables an intentional state to refer to one object rather than another is entirely between the ears of the referring subject. Internalism, so construed, has in recent decades been challenged by a series of arguments for the view that mental contents themselves are not in the head, or at least not entirely in the head, but in large part reside in relations between what is going on in the head and the rest of the world. It is important to see that this externalist theory is not merely claiming that our inner mental contents are often caused by external events (both sides agree on that) but rather that the contents themselves are not truly inner but are, at best, a mixture of the inner and outer. If that sounds vague, I am afraid it is, because externalism is a rather vaguely stated thesis.