on his ability as a thinker or his artfulness, on the familiarity or the pleasantness of the topie. Again, they would destroy the criterion by reasoning of this kind. Even the criterion has either been critically determined or not. If it has not, it is definitely untrustworthy, and in its purpose of distinguishing is no more true than raise. If it has, it will belong to the class of particular judgements, so that one and the same thing determines and is determined, and the criterion which has determined will have to be determined by another, that other by another, and so on ad infinitum. In addition to this there is disagreement as to the criterion, some holding that man is the criterion, while for some it is the senses, for others reason, for others the apprehensive presentation. Now man disagrees with man and with himself, as is shown by differences of laws and customs. The senses deceive, and reason says different things. Finally, the apprehensive presentation is judged by the mind, and the mind itself changes in various ways. Hence the criterion is unknowable, and consequently truth also. They deny, too, that there is such a thing as a sign. If there is, they say, it must either be sensible or intelligible. Now it is not sensible, because what is sensible is a common attribute, whereas a sign is a particular thing. Again, the sensible is one of the things which exist by way of difference, while the sign belongs to the category of relative. Nor is a sign an object of thought, for objects of thought are of four kinds, apparent judgements on things apparent, non-apparent judgements on things nonapparent, non-apparent on apparent, or apparent on non-apparent : and a sign is none of these, so