Aristotle Vs. Plato

Aristotle argued that particulars, not universals, are ultimately real. He connected particulars with a special term, "ousia", which itself means "reality", though it is usually translated as "substance". "What is substance?" (Cooper, 1999). Aristotle answered this question by defining a substance as an individual, existing thing. Such a "thing" is not merely a form, nor is it a hunk of matter. Instead, it must always combine matter and form within itself. Substance combines form and matter in such a way that the matter fulfils a necessary function, rather than being just an accident or illusion. For the material of a substance gives it its "distinctive mark", which is that, "while remaining numerically one and the same it, it is capable of admitting contrary qualities" through a material change (Cooper, 1999). For example, the pen I am now holding in my hand would still be an example of the substance of "pen" even if it changed from having the quality of blue pen into having the quality of a red pen. For Aristotle it is impossible that all individuals in a category be destroyed while the forms (ideals) still exist. This is because the forms exist only in matter, in the concrete individuals. .
             Aristotle's view to me is more persuasive then Plato's on the subject of the forms because we can never experience this world of forms, and therefore we cannot claim to have any knowledge of its existence. Plato's position lacks proof. He was making a metaphysical assumption based on reasoning: so where do our notions of categories and abstractions come from? When we see, for example, squares, we see all sorts of things that we call "square", but none of them really are so where do we get that idea? Plato's answer is that there is an ideal square somewhere that is the example, the paradigm, the ideal model, for all the imperfect squares we see, draw, imagine, etc. That perfect square, and the perfect triangle, and so forth, are the Forms.