spread over a far wider range.  He differed from Plato chiefly in relation to the doctrine of ideas, without however resolving the difficulty which divided them.  As he made matter to be the eternal ground of phenomena, he reduced the notion of it to a precision it never before enjoyed, and established thereby a necessary element in human science.  But being bound to matter, he did not soar, as Plato did, into the higher regions of speculation; nor did he entertain as lofty views of God or of immortality.  Neither did he have as high an ideal of human life; his definition of the highest good was a perfect practical activity in a perfect life.

With Aristotle closed the great Socratic movement in the history of speculation.  When Socrates appeared there was a general prevalence of scepticism, arising from the unsatisfactory speculations respecting Nature.  He removed this scepticism by inventing a new method of investigation, and by withdrawing the mind from the contemplation of Nature to the study of man himself.  He bade men to look inward.  Plato accepted his method, but applied it more universally.  Like Socrates, however, ethics were the great subject of his inquiries, to which physics were only subordinate.  The problem he sought to solve was the way to live like the Deity; he would contemplate truth as the great aim of life.  With Aristotle, ethics formed only one branch of attention; his main inquiries were in reference to physics and metaphysics.  He thus, by bringing these into the region of inquiry, paved the way for a new epoch of scepticism.

Both Plato and Aristotle taught that reason alone can form science; but, as we have said, Aristotle differed from his master respecting the theory of ideas.  He did not deny to ideas a subjective existence, but he did deny that they have an objective existence.  He maintained that individual things alone exist; and if individuals alone exist, they can be known only by sensation.  Sensation thus becomes the basis of knowledge.  Plato made reason the basis of knowledge, but Aristotle made experience that basis.  Plato directed man to the contemplation of Ideas; Aristotle, to the observation of Nature.  Instead of proceeding synthetically and dialectically like Plato, he pursues an analytic course.  His method is hence inductive,—­the derivation of certain principles from a sum of given facts and phenomena.  It would seem that positive science began with Aristotle, since he maintained that experience furnishes the principles of every science; but while his conception was just, there was not at that time a sufficient amount of experience from which to generalize with effect.  It is only a most extensive and exhaustive examination of the accuracy of a proposition which will warrant secure reasoning upon it.  Aristotle reasoned without sufficient certainty of the major premise of his syllogisms.