Plato"s theory of forms asserts that the non-material abstract form (or idea), and not the material world known to us through sensation, possess the highest and most fundamental kind of reality. This was supposed to be plato"s possible solution to the problem of universals. Plato"s forms are just that and nothing else (ex. Aristotle rejected plato"s theory of forms because he found that referring to what is predicated of all things as a this" leads to an infinite regress in plato"s theory of forms. Aristotle"s conception of forms involved using primary and secondary substances rather than. Forms" because all things in existence are substance (whether or not they are material or immaterial) Aristotle offers a distinction between primary ( a this" or particular) and secondary substances ( a sort of thing" or universal) The primary and secondary substances go hand in hand with one another and cannot exist without each other (primary substances belong to secondary substances)