With Socrates and Plato, scepticism exhibits itself under two new aspects: as an accompaniment of religious belief, and as an element of constructive thought. Thus they represent both the good and the bad side of this tendency: the aspect under which it is a help, and the aspect under which it is a hindrance to scientific investigation. With both philosophers, however, the restriction or negation of human knowledge was a consequence rather than a cause of their theological convictions; nor do they seem to have appreciated its value as a weapon in the controversy with religious unbelief. When Socrates represented the irreconcilable divergence in the explanations of Nature offered by previous thinkers as a sufficient condemnation of their several pretensions, he did not set this fact against the arguments by which a Xenophanes had similarly endeavoured to overthrow the popular mythology; but he looked on it as a fatal consequence of their insane presumption in meddling with the secrets of the gods. On one occasion only, when explaining to Euthydêmus that the invisibility of the gods is no reason for doubting their existence, he argues, somewhat in Butler’s style, that our own minds, whose existence we cannot doubt, are equally invisible.[222] And the Platonic Socrates makes it his business to demonstrate the universality of human ignorance, not as a caution against dogmatic unbelief, but as a glorification of the divine knowledge; though how we come to know that there is any such knowledge he leaves utterly unexplained. In Plato’s _Parmenides_ we have to note the germ of a new dialectic. There it is suggested that we may overcome the difficulties attending a particular theory—in this instance the theory of self-existing ideas—by considering how much greater are the difficulties which would ensue on its rejection. The arguments advanced by Zeno the Eleatic against the reality of motion are mentioned as a case in point; and Plato proceeds to illustrate his proposed method by showing what consequences respectively follow if we first assume the existence, and then the non-existence of the One; but the whole analysis seems valueless for its immediate purpose, since the resulting impossibilities on either side are left exactly balanced; and Plato does not, like some modern metaphysicians, call in our affections to decide the controversy.