ONE:Plotinus follows up his essay on the Virtues by an essay on Dialectic.498 As a method for attaining perfection, he places dialectic above ethics; and, granting that the apprehension of abstract ideas ranks higher than the performance of social duties, he is quite consistent in so doing. Not much, however, can be made of his few remarks on the subject. They seem to be partly meant for a protest against the Stoic idea that logic is an instrument for acquiring truth rather than truth itself, and also against the Stoic use or abuse of the syllogistic method. In modern phraseology, Plotinus seems to view dialectic as the immanent and eternal process of life itself, rather than as a collection of rules for drawing correct inferences from true propositions, or from propositions assumed to be true. We have seen how he regarded existence in the334 highest sense as identical with the self-thinking of the absolute Nous, and how he attempted to evolve the whole series of archetypal Ideas contained therein from the simple fact of self-consciousness. Thus he would naturally identify dialectic with the subjective reproduction of this objective evolution; and here he would always have before his eyes the splendid programme sketched in Plato��s Republic.499 His preference of intuitive to discursive reasoning has been quoted by Ritter as a symptom of mysticism. But here, as in so many instances, he follows Aristotle, who also held that simple abstraction is a higher operation, and represents a higher order of real existence than complex ratiocination.500Notwithstanding the sterility commonly associated with mere negation, it was this which, of all the later Greek schools, possessed the greatest powers of growth. Besides passing through more than one stage of development on its own account, Scepticism imposed serious modifications on Stoicism, gave birth to Eclecticism, and contributed to the establishment of Neo-Platonism. The explanation is not far to seek. The more highly organised a system is, the more resistance does it offer to change, the more does its transmission tend to assume a rigidly scholastic form. To such dogmatism the Sceptics were, on principle, opposed; and by keeping the problems of philosophy open, they facilitated the task of all who had a new solution to offer; while mind and its activities being, to some extent, safe from the universal doubt, the sceptical principle spontaneously threw back thought on a subjective instead of an objective synthesis of knowledge��in other words, on that psychological idealism the pregnancy and comprehensiveness of which are every day becoming more clearly recognised. And we shall now see how the same fertilising power of criticism has been manifested in modern times as well.