Thus Platonism and its way of treating narrative could not but foster the allegorical interpretation of ancient tradition and literature, which was already in vogue in Plato’s time. It mattered not that he would have nothing to do with the current allegories through which men moralized or rationalized the old tales of the doings of the gods. He was himself a weaver of the loveliest allegories when it served his purpose. And after him the allegorical habit entered into the interpretation of all ancient story. In the course of time allegory will be applied by the Jew Philo of Alexandria to the Pentateuch; and one or two centuries later it will play a great rôle in Christian polemics against Jew and then against Manichean. It will become _par excellence_ the chief mode of patristic exegesis, and pass on as a legacy of spiritual truth to the mediaeval church. Aristotle strikes us as a man of different type from Plato. Whether his intellectual interests were broader than his teacher’s is hardly for ordinary people to say. He certainly was more actively interested in the investigation of nature. Head of an actual school (as Plato had been), and assisted by the co-operation of able men, he presents himself, with what he accomplished, at least in threefold guise: as a metaphysician and the perfecter, if not creator, of formal logic; as an observer of the facts of nature and the institutions and arts of men; as a man of encyclopaedic learning. These three phases of intellectual effort proportioned each other in a mind of universal power and appetition. Yet it has been thought that there was more metaphysics and formal logic in Aristotle than was good for his natural science. The lost and extant writings which have been ascribed to him, embraced a hundred and fifty titles and amounted to four hundred books. Those which have been of universal influence upon human inquiry suffice to illustrate the scope of his labours. There were the treatises upon Logic and first among them the _Categories_ or classes of propositions, and the _De interpretatione_ on the constituent parts and kinds of sentences. These two elementary treatises (the authorship of which has been questioned) were the only Aristotelian writings generally used through the West until the latter half of the twelfth century, when the remainder of the logical treatises became known, to wit, the _Prior Analytics_, upon the syllogism; the _Posterior Analytics_ upon logical demonstration; the _Topics_, or demonstrations having probability; and the _Sophistical Elenchi_, upon false conclusions and their refutation. Together these constitute the _Organon_ or complete logical instrument, as it became known to the latter half of the twelfth century, and as we possess it to-day.