I wish to give some critical remarks towards the metaphysics and epistemology of Aristotle in regard to universals. Aristotle wishes to do justice to both universality and particularity. He tries to improve on the Platonist program. He sees the issue with this two-world ontology. Aristotle saw how difficult it is to account for knowledge of the perfect forms in an imperfect world of becoming. So, he merely brings the forms over into this world and places them in the particular.
He keeps and modifies Plato’s form/matter distinction. The forms are not independent of the world, but rather reside in the things of the world. The most basic category of this worldview is substance. Substance is comprised of both form and matter. The form tells us what a thing is and the matter distinguishes it(some call it “thisness”).
Reality becomes two diametrically opposed things. We have rational forms and the becoming matter. There we have to discuss the actuality/potentiality distinction. The example of the acorn is that it is actually an acorn(it has the forms and essence of being an acorn), but it must also have the potentiality to become a tree(an unrealized treeness). Matter is not not to be thought of in terms of atomic theory(to which individual little things make up objects). It is an unrealized form. As they become actualized an object begins to change and take a new form in this evolutionary developing world.
The other thing that must be recognized is that Aristotle was an ancient empiricist. The laws of logic may be known through intuition, but substances were known from sense experience. Knowledge is characterized by knowing the forms and not by knowing matter. This is something Aristotle kept from Plato.
It seems to me that Aristotle’s view has various issues. In his scheme, we come to knowledge by attraction(from sense experience) and intuition. These mechanisms are known for their inherently subjective character. People have different intuitions and we each perceive objects differently. Suppose we have a case where a person has the ability to see one extra color that normal people see. This color(form) would be abstracted from the same particular, but with completely different interpretations. Is the form really in the thing? Or is it in the mind?
The nature of forms themselves start from a commonsensical proposal and radically change once examined. We don’t see a connection between these objects. In fact, we see one red object and then another, but we actually don’t see the connection between these things. We see multiple red objects, but why should we provide any connection between the red that they exemplify?
The implication also seems to lead us to a bit of Neo-Platonism. In Aristotle, you have a spectrum of being and non-being. This is known as the great chain of being. The more you exist is the more you participate with abstract form. The more things that drift away from pure form is the more to drift into matter and potentiality(non-being). This is similar to Plotinus in that all being is an emanation from the “One”. Which is the ultimate reality just like the “Pure Form” is for Aristotle.
Dr. John Frame also had an interesting criticism in his work on the history of Philosophy:
Form and matter are usually relative. In a brick, clay is matter and the form is its brickness, the qualities that make it a brick rather than something else. But when the brick is used to build a house, the brick itself can be considered matter and the house itself (or rather its houseness) is the form. So the brick is form in one relationship, matter in another. Yet it seems that there must be some kind of absolute matter or prime matter. The house is made of bricks; the bricks are made of clay; the clay is made of various other things. Each of these can be described as a form, because each is a substance, bearing various qualities. But this sequence cannot go to infinity. Let’s say that we reach the smallest possible particle, perhaps one of Democritus’s atoms. What is that made of? Presumably a kind of matter that has no qualities, but that is only a bearer of qualities. But something without qualities is not a substance. It is nothing. Thus the matter that underlies all reality, the stuff of which all reality is made, is indistinguishable from nonbeing. Aristotle avoids saying that, but the consequence is hard to avoid. Aristotle insisted that such prime matter is not actually found in nature. In the natural world, there are only substances, and matter exists only in conjunction with form. But the problem reoccurs in every substance. For in every case we must ask: what is the form the form of? What is the stuff that the forms are attached to? And the answer must be, ultimately, nothing.