Thomas Reid draws a distinction between the social and solitary operations of mind—acts of mind that require other intelligent beings versus those that may performed on one’s own. Yet his distinction obscures the irreducibly social character of the solitary operations. This paper preserves Reid’s distinction while accommodating the social character of the solitary operations. According to Reid, the solitary operations presuppose the social operations, expressed in what he calls the ‘natural language’ of mankind—a language that communicates the intentions that give (...) rise to the agreements by which the conventions of artificial languages are developed. Using artificial languages, we begin to sort the world into kinds and to anticipate the regular events that make a practical difference in our lives, providing the general conceptions that give our trains of thought the order and regularity required to form the solitary operations. By using artificial languages, we adapt social operations to solitary ends, to think alone and in silence. (shrink)