Abstract

In this paper I examine the foundations of physical externalism and social externalism and argue that these foundations are incompatible. Physical externalism is based on a direct reference theory of natural-kind terms, while social externalism is based on a description theory of natural-kind terms. Thus, physical externalism and social externalism are incompatible just in the same way that the direct reference theory of proper names is incompatible with the description theory of proper names. My argument will proceed as follows. In Section One, I shall explain what the two theses say and spell out my suspicion. In Section Two, I shall take a look at the initial setups for physical externalism and social externalism by examining Putnam’s and Burge’s original arguments. Finally in Section Three, I shall explain that the real incompatibility comes to lie in the different assumptions on which the two theories are based. I will present some thought experiments to highlight this incompatibility.