In describing the ancient dialectic Smith had to give an explanation of what Plato meant by “ideas.” The later Platonists imagined their master to mean no more than that “the Deity formed the world after what we would now call an idea or plan conceived in his own mind, in the same manner as any other artist.” Against them the young philosopher proceeded to turn the formidable battery of ratiocination that was one day to demolish a living and formidable foe. It is characteristic of Adam Smith that whether he is attacking the harmless errors of an extinct school of thought, or the noxious fallacies of an established policy, he tries every mode of assault. He “swims, or sinks, or wades, or creeps, or flies”:— “If Plato had meant to express no more than this most natural and simple of all notions, he might surely have expressed it more plainly, and would hardly, one would think, have talked of it with so much emphasis, as of something which it required the utmost reach of thought to comprehend. According to this representation, Plato’s notion of species, or Universals, was the same with that of Aristotle. Aristotle, however, does not seem to understand it as such; he bestows a great part of his Metaphysics upon confuting it, and opposes it in all his other works.” Again, this notion of the separate existence of Species is the very basis of Plato’s philosophy; and there is not a single dialogue in all his works which does not refer to it. Can Aristotle, “who appears to have been so much superior to his master in everything but eloquence,” wilfully have misinterpreted Plato’s fundamental principle when Plato’s writings were in everybody’s hands and his disciples were spread all over Greece; when Speusippus, the nephew and successor of Plato, as well as Xenocrates, who continued the school in the Academy, at the same time as Aristotle held his in the Lyceum, must have been ready at all times to expose and affront him for such gross disingenuity? Aristotle’s interpretation had been followed by Cicero, Seneca, and every classical authority down to Plutarch, “an author who seems to have been as bad a critic in philosophy as in history, and to have taken everything at second-hand in both.” Whether Smith either then or at any time arrived at metaphysical certainty is very doubtful. “To explain the nature, and to account for the origin of general Ideas is,” he says, “even at this day, the greatest difficulty in abstract philosophy.”