SPROUL: In this schema, Immanuel Kant made a distinction that has perhaps been more famous
than anything else that he’s done and perhaps more significant than anything else that he’s done.
That is, he distinguishes between two realms. One is called the “noumenal realm,”
and the other is called the “phenomenal realm.” Now, the phenomenal realm is the realm
of sensations. It is the realm of appearances. It is the concrete material realm where the
scientist is engaged in his exploration and in his inquiry. It is the realm where sensations
occur. So, we might call it the “sensational realm.” It’s sensational not in the sense of
“fantastic” or “exciting,” but sensational in a more literal sense—in the sense that
it is the realm in which we have sensations or perceptions of physical things, the external world
to us. And the phenomenal world is basically the arena of investigation for the scientist.
The scientist is exploring and measuring and experimenting with things that he can perceive.
Now, the noumenal realm is the realm of metaphysics. And for Kant, there are three
things that he puts in the noumenal world—that is, three notions or categories. They are God,
the self, and what he calls the “der wesentliche” or what we would call the essences.
Let’s look at those in reverse order. What he’s speaking about as essences
are those metaphysical realities that all of the previous philosophers have been struggling
with with their concepts of substance or the substratum. Remember when we looked at Locke,
and Locke made a distinction between primary and secondary qualities. And then, Berkeley challenged
that saying that all the qualities were secondary. And we remember Aquinas and his distinction—or
Aristotle and his distinction between substance and accidents. Everybody assumes
that there is some kind of substratum of reality that exists beyond what we can perceive.
There are real essences. For Plato, those essences were the ideas that are the eternal ideas.
For Aristotle, they inhere in objects themselves. But whether you are a Platonist
or an Aristotelian, you still had some concept of substance—some ontology—some sense of being.
But Kant is saying you never have a perception of substance. You never have a sensation
of essence or of being. All that we can perceive are the external manifestations of these things.
And so, we can’t know what that essence is. In fact, we can’t even know that there is an
essence that underlies these perceptions. That doesn’t mean that he didn’t believe
in essences or in substances. What he’s saying is we can't know them.
He is agnostic about them, claiming that science cannot learn anything about essences
so we might as well abandon any pursuit of them. And metaphysics becomes
more and more speculative and less and less scientific as long as it’s trying to go to the
meta-realm—to the realm beyond physics into the metaphysical realm trying to get to this essence.