Is
God's Existence Self-Evident?
In
partial opposition to his first objection's contention that the first
principles of a science -- in the Aristotelian sense of "science" --
must be self-evident, Aquinas opens his response in ST Part I Question 2,
Article 1 by drawing a distinction. Though the first principles are always
self-evident in themselves, he
argues, they are "sometimes self-evident to us and sometimes not."[1] The
basis for his distinction is located in the claim that a proposition is
self-evident only if the predicate term forms part of the meaning for a subject
term. The example he uses to illustrate the idea he has in mind is that
"human beings are animals," since being human entails, in the sense
of the meaning of the subject term "human being," being an animal.
However,
he also claims, some propositions are such that not everyone has knowledge, in
the sense of self-evident knowledge, of the meanings in virtue of which the
subject term contains or logically implies a specific predicate meaning. For
example, as he cites from Boethius, there are some propositions the meaning of
which are "self-evident only to the learned"; here, the example he
uses is "that what isn't a body won't occupy space," the subject of
which, presumably, is "body" in terms of its meaning. With this
distinction in mind, then, he argues that the proposition "God
exists," while self-evident in itself, is not self-evident to us.
One
point worth touching on here before proceeding to article 2 is Aquinas's reason
for rejecting the idea that one can know that God exists merely by knowing the
meaning of the subject term "God." The preliminary suggestion Aquinas
gives for rejecting the idea is that not everyone understands the word
"God" to mean "that than which nothing greater can be
conceived." But the much more serious consideration he advances, I think,
is that, even granting that "God" had this commonly accepted meaning,
it would not follow that something matching this description exists, unless someone
were forced, on the pain of contradiction, to concede it as true. But it seems
that someone can reject that "God" has such a meaning without seeming
to contradict themselves in the process. At the same time, it is arguable that Aquinas
does not have good grounds for objecting to a demonstration for God's existence in this exact way. If he has just conceded that the proposition "God exists"
is self-evident in itself, he has also just conceded that God's existence is self-evident.
So, in principle, he does not have good reasons for objecting to an argument for
God's existence on, as one might say, ontological grounds; though he may still object to such an argument on epistemic
grounds, e.g., that God's existence is not self-evident to us.
Can
One Prove that God Exists?
However,
the strictures that Aquinas sets in place concerning the knowledge of God's
existence might seem to raise the question of how one could even begin to
acquire such knowledge, since this knowledge seems to require a scientific
demonstration (in the Aristotelian sense of a science) and Aquinas holds that a
demonstration in this sense requires the definition for a subject. Aquinas
shows that he is at least somewhat aware of this in his effort to address an
opinion from John Damascene, an authority whom Aquinas respects, that we cannot
know what God is, but only what God is not. But it is worth noting that this
concern would still exist without an endorsement of Damascene's negative
theology, considering that Aquinas has already denied that one can have
knowledge concerning God's existence simply in virtue of knowing the meaning of
the subject term "God" and the predicate term "exists." And
this last denial seems to amount to an admission that we are incapable of having knowledge of God's definition.
In
response to this last difficulty, Aquinas answers that what we generally take
God's name to mean can take the place
of God's definition with respect to the middle term normally required for a formal
demonstration. The grounds he claims for this view are that for existence
claims, i.e., whether a thing exists, the central link required for a proper
demonstration is not a thing's definition but its name, which, Aquinas argues,
"derives from its effects." Appropriately, then, he claims that there
are two distinct forms of demonstration: a demonstration from the cause to the
effect and a demonstration of the effect to the cause. The first demonstrates,
he argues, "why things are as they are," and relies (presumably) on
the definitions or meanings of their subject terms. The second demonstrates
"how things are," since, from any effect, he contends, one "can
demonstrate that its cause
exists."
However,
this approach can seem rather circular, owing to the fact that one might
question whether, in this case at least, from the fact that one can demonstrate
of something "that its cause exists" one can also know "that its
cause is God." The problem is that it is not clear how one can identify
God as "the cause" without having some prior understanding or idea,
however slight, of what God is. Denying that we can have such knowledge,
Aquinas proposes to rely on God's name as the middle term of the syllogism. One
not unimportant question, however, is how the name of God, in the exact
sense Aquinas needs for an Aristotelian demonstration, is itself known, i.e., by revelation, is known by all, etc. If this is the case, and if there is no other way of
coming to know the meaning Aquinas has in mind, one cannot have knowledge of
God's existence apart from revealed knowledge. Perhaps he does not think that one
can know about God apart from revelation, but this does seem like a very likely
explanation. And nowhere else -- to my knowledge -- does Aquinas offer an explanation for how one can come to know the meaning of the name "God" in either the sense of the proper name "God" or in the sense of the "divine names," such as First Cause, Prime Mover, etc.
Te
Velde suggests that Aquinas may presume there to be a single meaning of the name
"God," which, in its essentials, is the same for all, regardless of
whether they are "Christians, Jews, Muslims, or pagans."[2]
Whatever the merits of this proposal, the difficulty with this is that Aquinas
has already rejected, in his response to the idea that one can know that God
exists from the meaning of the word "God," that "God" has
such a universally recognized meaning.
I thus conclude that even though one might possibly consider the actual arguments Aquinas offers for proving the existence of God as a notable contribution to natural theology, one does not have good grounds for regarding his underlying "program" for natural theology, i.e., that which he offers in ST q.2 articles 1 and 2, as workable without some further development.
I thus conclude that even though one might possibly consider the actual arguments Aquinas offers for proving the existence of God as a notable contribution to natural theology, one does not have good grounds for regarding his underlying "program" for natural theology, i.e., that which he offers in ST q.2 articles 1 and 2, as workable without some further development.
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