‘Empirical realism’ is the position that the existence of the external world is supported by experience in much the way that any scientific theory is supported by observational data. The empirical realist reply to skepticism has recently been extended by Paul Ziff from skepticism about material objects to skepticism about other minds (Ziff, 1965). I do not suggest that Ziff was unaware of the need for the various qualifications that have to be made in the realist position if it is to be tenable. However, I am not happy with the way in which Ziff states the arguments. Ziff's statements are very brief, and it may be that the features I shall object to are ones that he would have eliminated in a longer and less aphoristic presentation. However, here they are.

There are two parts to Ziff's argument: what he calls the via negativa, and the citation of positive support. I take them up in turn.

The via negativa amounts to this: if I accept the hypothesis that I alone have a mind, then I must, according to Ziff, suppose that I differ from other human beings in some other respect, presumably a physiological respect. I can't differ from other human beings in just this one way, that I have a mind and they don't.