Published online by Cambridge University Press: 25 February 2009
In ordinary life everyone assumes that he has a great deal of knowledge about other minds or persons. This assumption has naturally aroused the curiosity of philosophers; though perhaps they have not been as curious about it as they ought to have been, for they have devoted many volumes to our consciousness of the material world, but very few to our consciousness of one another. It was thought at one time that each of us derives his knowledge of other minds from the observation of other human organisms. I observe (it was said) that there are a number of bodies which resemble my own fairly closely in their shape, size, and manner of movement; I conclude by analogy that each of these bodies is animated by a
page 430 note 1 I use a phrase “a foreign body” to mean “a body other than my own.” As we shall see, it need not be a human body.
page 440 note 1 This is said to have happened in ancient Athens even in classical times.
page 447 note 1 Here we may note that even the most rigorous course of Cartesian doubt requires the use of symbols. One cannot doubt without symbols to bring before one's mind the proposition which is to be doubted. And philosophical doubt, which is concerned with complicated and highly abstract matters, is scarcely conceivable without the use of verbal symbols. We may conjecture that Descartes himself conducted his doubt in French, with some admixture of Latin.