Scepticism, as a philosophical principle, is alien from early Greek thought; but it is pervaded by a negative tendency exhibited in four different directions, all converging towards the later attitude of suspensive doubt. There are sharp criticisms on the popular mythology; there are protests against the ascription of reality to sensible appearances; there are contemptuous references on the part of some philosophers to the opinions held by others; and there are occasional lamentations over the difficulty of getting at any truth at all. The importance, however, of these last utterances has been considerably exaggerated both in ancient and modern times. For, in some instances, they are attributable solely to the distrust of sense-perception, and in others they seem to express nothing more than a passing mood against which we must set the dogmatic conclusions elsewhere enunciated with perfect confidence by the same thinkers.[219] At the same time, we have to note, as an illustration of the standing connexion between theological belief and that kind of scepticism which is shown by distrust in man’s power of discovering the truth for himself, that the strongest expressions of such a distrust are to be found in the two most religious of the pre-Socratic thinkers, Xenophanes and Empedocles. III. A new period begins with the Greek Humanists. We use this term in preference to that of Sophists, because, as has been shown, in specially dealing with the subject, half the teachers known under the latter denomination made it their business to popularise physical science and to apply it to morality, while the other half struck out an entirely different line, and founded their educational system on the express rejection of such investigations; their method being, in this respect, foreshadowed by the greatest poet of the age, who concentrates all his attention on the workings of the human mind, and followed by its greatest historian, with whom a similar study takes the place occupied by geography and natural history in the work of Herodotus. This absorption in human interests was unfavourable alike to the objects and to the methods of previous enquiry: to the former, as a diversion from the new studies; to the latter, as inconsistent with the flexibility and many-sidedness of conscious mind. Hence the true father of philosophical scepticism was Protagoras. With him, for the first time, we find full expression given to the proper sceptical attitude, which is one of suspense and indifference as opposed to absolute denial. He does not undertake to say whether the gods exist or not. He regards the real essence of Nature as unknowable, on account of the relativity which characterises all sensible impressions. And wherever opinions are divided, he undertakes to provide equally strong arguments for both sides of the question. He also anticipates the two principal tendencies exhibited by all future scepticism in its relation to practice.