I now pass to the POLEMICAL handling of the metaphysical subjects. We owe to the Greeks the study of philosophy through methodised debate; and the state of scientific knowledge in the age of the early Athenian schools was favourable to that mode of treatment. The conversations of Socrates, the Dialogues of Plato, and the Topics of Aristotle, are the monuments of Greek contentiousness, turned to account as a great refinement in social intercourse, as a stimulus to individual thought, and a means of advancing at least the speculative departments of knowledge. Grote, both in his "Plato," and in his "Aristotle," while copiously illustrating all these consequences, has laid extraordinary stress on still another aspect of the polemic of Socrates and Plato, the aspect of _free-thought_, as against venerated tradition and the received commonplaces of society. The assertion of the right of private judgment in matters of doctrine and belief, was, according to Grote, the greatest of all the fruits of the systematised negation begun by Zeno, and carried out in the "Search Dialogues" of Plato. In the "Exposition Dialogues" it is wanting; and in the "Topica," where Eristic is reduced to method and system by one of Aristotle's greatest logical achievements, the freethinker's wings are very much clipt; the execution of Socrates probably had to answer for that. It is to the Platonic dialogues that we look for the full grandeur of Grecian debate in all its phases. The Plato of Grote is the apotheosis of Negation; it is not a philosophy so much as an epic; the theme--"The Noble Wrath of the Greek Dissenter". At all times, there is much that has to be achieved by solitary thinking. Some definite shape must be given to our thoughts before we can submit them to the operation of other minds; the greater the originality, the longer must be the process of solitary elaboration. The "Principia" was composed from first to last by recluse meditation; probably the attempt to discuss or debate any parts of it would have only fretted and paralysed the author's invention. Indeed, after an enormous strain of the constructive intellect, a man may be in no humour to have his work carped at, even to improve it. In the region of fact, in observation and experiment, there must be a mass of individual and unassisted exertion. The use of allies in this region is to check and confirm the accuracy of the first observer. Again, an inquirer, by dint of prolonged familiarity with a subject, may be his own best critic; he may be better able to detect flaws than any one he could call in. This is another way of stating the superiority of a particular individual over all others in the same walk. Such a monarchical position as removes a man alike from the rivalry and from the sympathy of his fellows, is the exception; mutual criticism and mutual encouragement are the rule. The social stimulants are of avail in knowledge and in truth as well as everything else.