 In the philosophy of mind, externalism is the view that what is going on in an individual’s mind is not (entirely) determined by what is going on inside her body, including her brain. Externalism comes in two principal forms: externalism about mental content and externalism about the vehicles or bearers of that content. The latter form of externalism is commonly known as the extended mind. At stake are important issues concerning the nature of the mind and its relation to the world, both natural and social.