Externalism is a group of positions in the philosophy of mind which argues that the conscious mind is not only the result of what is going on inside the nervous system (or the brain), but also what occurs or exists outside the subject. It is contrasted with internalism which holds that the mind emerges from neural activity alone. Externalism is a belief that the mind is not just the brain or functions of the brain.
There are different versions of externalism based on different beliefs about what the mind is taken to be. Externalism stresses factors external to the nervous system. At one extreme, the mind could possibly depend on external factors. At the opposite extreme, the mind necessarily depends on external factors. The extreme view of externalism argues either that the mind is constituted by or identical with processes partially or totally external to the nervous system.
Another important criterion in externalist theory is to which aspect of the mind is addressed. Some externalists focus on cognitive aspects of the mind – such as Andy Clark and David Chalmers,Shaun Gallagher and many others – while others engage either the phenomenal aspect of the mind or the conscious mind itself. Several philosophers consider the conscious phenomenal content and activity, such as William Lycan, Alex Byrne or Francois Tonneau; Teed Rockwell or Riccardo Manzotti. ## Semantic externalism
Semantic externalism suggests that the mental content does not supervene on what is in the head. Yet the physical basis and mechanisms of the mind remain inside the head. This is a relatively safe move since it does not jeopardize our beliefs of being located inside our cranium. Hilary Putnam focused particularly on intentionality between our thoughts and external state of affairs – whether concepts or objects. To defend his position, Putnam developed the famous Twin Earth thought experiment. Putnam expressed his view with the slogan “‘meanings’ just ain’t in the head.”
In contrast, Tyler Burge emphasized the social nature of the external world suggesting that semantic content is externally constituted by means of social, cultural, and linguistic interactions. ## Phenomenal externalism
Phenomenal externalism extends the externalist view to phenomenal content. Fred Dretske (Dretske 1996) suggested that “The experiences themselves are in the head (why else would closing one’s eyes or stopping one’s ears extinguish them?), but nothing in the head (indeed, at the time one is having the experiences, nothing outside the head) need have the qualities that distinguish these experiences.” (Dretske 1996, p. 144-145). So, although experiences remain in the head, their phenomenal content could depend on something elsewhere.
It has been often held that some, if not all, of mental states must have a broad content, that is an external content to their vehicles. For instance, Frank Jackson and Philip Pettit stated that “The contents of certain intentional states are broad or context-bound. The contents of some beliefs depend on how things are outside the subject” (Jackson and Pettit 1988, p. 381)
However, neither Dretske nor Lycan go far as to claim that the phenomenal mind extends literally and physically beyond the skin. In sum they suggest that phenomenal contents could depend on phenomena external to the body, while their vehicles remains inside.