THE SOUL
The
distinction between actuality and potentiality, the principle that effects are
contained in their causes either “formally” or “eminently,” and that final
causality pervades the natural order, in fact have the most dramatic
consequences for the debate between religion and atheism.
We want now
to examine how some of these principles were applied by Aquinas and the
Scholastic tradition in general to a defense of the immortality of the soul and
the natural law conception of morality.
The Soul
For Aristotle a soul is
just the form or essence of a living thing. One should not think of some
ghostly object of the sort that floats away from a body after death. The soul
is just a kind of form.
The soul of a plant is what Aristotelians call a “nutritive
soul”; and that is just a form or essence that gives a thing that has it the
powers of taking in nutrients, growing, and reproducing itself.
The soul of a non-human animal is called a “sensory soul”
and it is just a form or essence that gives
a thing that has it both the powers of a nutritive soul, and also an
animal’s distinctive powers of being able to sense the world around it and to
move itself.
When we come to human beings we have what is called a
“rational soul” which includes both the powers of the nutritive and sensory
souls and also the distinctively human powers of intellect and will. So there
is a natural hierarchical relationship between the souls.
A thing having certain form goes hand in hand with its
having a certain final cause or natural end. A human being has all the ends of
the sensory and nutritive soul, but on top of them he has the ends or final
causes entailed by being rational and having free will. Rationality has its
natural end or final cause in the attainment of truth. Free will has as its
natural end or final cause the choice of those actions that best accord with
the truth about the human nature being’s own nature or essence.
Morality, according to Aristotle and Aquinas, is the
habitual choice of actions that further the hierarchically ordered natural ends
entailed by human nature. We have seen that the deepest truth about the world
is that it is caused and sustained by God. The highest fulfillment then of the
power of the intellect then is to know God. The highest fulfillment of free
choice is to live in a way that facilitates the knowing of God.
The power of the intellect cannot possibly require a
material or bodily organ for its operation. Central to the intellect’s
operation is its grasp of forms, essences, or universals, and other
abstractions like propositions. The immaterial nature of these things entails
that the intellect which grasps them must itself be immaterial as well. How so?
We apprehend the ‘universals’. The form of “dogness” that
exists in our minds when we think about dogs is the same form that exists in
actual dogs. This is grasping what they are. What they are is determined by
their essence or form. If the intellect is a material thing—some part of the
brain, then for the form to exist in the intellect is for the form to exist in
a certain material thing; for example, for the form of “dogness” to exist in a
certain parcel of matter is just for that parcel of matter to be a dog. In that
case, if your intellect was just the same thing as some part of your brain, it
follows that that part of your brain would become a dog whenever you thought
about dogs. “But that’s absurd!” Assuming that the intellect is material leads
to such absurdity; hence the intellect is not material.
The thought we are having must be as determinate as
triangularity itself, otherwise it just wouldn’t be a thought about
triangularity per se, but only a thought about some approximation of
triangularity. Material triangularity is only ever an approximation. It follows
that the thought about triangularity is not material. Suppose a thought about
triangularity consist of some physical representation in the brain somewhere
(in the form of a neuronal firing pattern or some such thing). Like any other
physical representation of a triangle, this one too would be just one
particular material thing among others, not universal at all. Again the idea
that thought is a purely a material operation of the brain makes no sense.
Aquinas’s claim isn’t a “soul of the gaps” analogue to “God
of the gaps” arguments. He is not speculating that there might be some ghostly
objet floating around in there. He is saying that given the facts about
universals, and our thoughts about them, it is conceptually impossible (not merely improbable) for the intellect
to be material. One thing neuroscience won’t “discover” is that thought is a
material operation of the brain, any more than it will “discover” that 2+2=5.
The soul of a man is not a complete substance; only the soul
and body (i.e. the form and matter) together constitute a thing or substance,
that is, a man. It is the man himself who thinks, just as it is the man himself
and not the soul who grows taller, digests his food, and walks around. For this
reason human thoughts correlate with certain brain events even if it is not
identical to any of them. The operation of the intellect and will constitute
the formal-cum-final cause of the action, of which the firing of the neurons,
flexing of the muscles, are the material cause.
The intellect itself operates without bodily organ, it does
depend indirectly on the senses for the raw material from which it abstracts
universals or essences (triangularity from particular triangles). The soul as
it does in thought can function apart from the matter it informs, then it can
also exist apart from the matter it informs, as a kind of incomplete substance.
Potentiality can never exist without actuality; but actuality can and does
exist without potentiality, namely in God who is pure actuality.
Similarly matter can never exist without form; but form can
exist without matter, and does in this case, at least after death, when the
matter of the body is not longer inform by the soul, its form. The soul as it does, partially operating and
thus existing as it does apart from the body even when informing it, does not
thereby die. For a thing to perish is just for it to lose its form. But the
soul doesn’t lose its form, because it is
a form.
