Aristotle refutes Plato's Theory of Ideas on three basic grounds: that the existence of Ideas contradicts itself by denying the possibility of negations; that his illustrations of Ideas are merely empty metaphors; and that they theory uses impermanent abstractions to create examples of perception. Though the theory is meant to establish concrete standards for the knowledge of reality, Aristotle considers it fraught with inconsistencies and believes that the concept of reality depends upon all forms' …showed first 75 words of 1332 total…

…showed last 75 words of 1332 total…and often dependent upon the observer. In general, Aristotle refutes Plato on the grounds that his Theory of Ideas tries too hard to establish concrete, universal definitions for things that depend too much on the material. Though both thinkers agree on the separation of the material and immaterial (which gave both a somewhat similar view of God), they still differ sharply over the permanence of standards by which human nature and endeavor can be judged.