The study of reality and existence is metaphysics, named from a set of books written by Aristotle asking what is being, what are first causes, and what is change. It studies what we are and what our purpose is, seeking knowledge about everything from the nature of the entire universe to that of he human mind.
Starting with Plato I think will make it much easier to understand the theories of his student Aristotle, later on.
Plato wanted to understand the relationship between the material and immaterial realms, the one and the many, change and permanence and the proper role of both senses and the intellect in coming to know them. He sought to demonstrate that objective knowledge about all these things, and not mere opinion, was possible. This is enshrine in his famous theory of Forms.
(For a fine
introduction to Plato’s thought in general and his Theory of Forms in
particular, see David Melling, Understanding
Plato (Oxford University Press, 1987)
What is a “Form”?
Consider
several triangles; on paper, on chalkboard, on sand, on the pc screen, small,
large, red, black.
The essence
or nature of a triangle is a closed plane figure with three straight sides.
The
features of a triangle has nothing to do with ‘triangularity” as such.
Every
particular physical or material triangle—the sort of triangle we know through
the senses, and indeed the only sort we can know through the senses—is always
going to have features that are simply not part of the essence of nature of
triangularity per se, and is always going to lack features that are part of the
essence or nature of triangularity.
Plato would
say that when we grasp the nature of being a triangle, what we grasp is not something material or physical, and
not something we grasp or could grasp through the senses.
Material triangles come and go but
triangularity stays the same.
The
essential features of triangles would remain true even if every particular
material triangle were erased tomorrow.
What we
know when we know the essence of triangularity is something universal
rather than particular, something immaterial rather than material, an something we know through the intellect
rather than senses.
What we
know is an objective fact that we have
discovered, not invented. It is not up to us to decide what the feature of
a triangle should be. If the Canadian parliament should declare that triangles should sometimes regarded has
having four sides, it would cast doubt on the sanity of the parliamentarians.
The Pythagorean theorems were true long before we discovered them and will
remain true long after we’re all dead.
Now if the essence of triangularity is
something neither material nor mental—that is to say, something that exists
neither in the material world nor merely in the human mind—then it has a unique
kind of existence all its own, that of an abstract object existing in what
Platonists sometimes call a “third realm.” And what is true, of the essences of
triangles is no less, true in Plato’s view, of the essences of pretty much everything; of squares, circles, and
other geometrical figures, but also (and more interestingly) of human beings,
tables and chairs, dogs, cats, justice, beauty, goodness, and so on and on.
When we grasp the essence of any of
these things, we grasp something that is
universal, immaterial, extra-mental, and known via the intellect rather
than senses, and is thus a denizen of this “third realm”. What we grasp, in
short, is a Form.
The Forms not being material
cannot exist in a spatial location. Plato’s whole point is that the Theory of
Forms, if correct, proves that there
is more to reality than the world of time and space. As Plato sees it our
senses are not the only sources of knowledge of reality; for the highest level
of reality is knowable only through the intellect.
In general,
the world of material things is merely a faint copy of re realm of the Forms. Particular things an events are what they
are only by “participating in,” or “instantiating” the Forms.
Fido is a
dog because it participates in the Form of dog.
Paying your
phone bill is a just action because it participates in the Form of Justice.
These
individual exemplars are all imperfect in various ways.
The Forms are perfect, being the archetypes
or standards by reference to which we judge something to be a dog or just
action, etc.
Individual
things come and go; the Forms, being
outside of time and space, are eternal and unchanging.
The Forms are more real that the
material things that exemplify them.
A shadow or
reflection won’t exist at all unless a physical object casts it, while the
object will exist whether or not its shadow or image does. By the same token,
the physical objects themselves exist only insofar as they participates in the
Forms, while the Forms would exist whether or not the particular physical instantiations
did.
