Let us first consider what is meant by "wisdom." A man may be wise in some particular pursuit,
such as making houses; this implies that he knows the means to some particular end. But all
particular ends are subordinate to the end of the universe, and wisdom per se is concerned with
the end of the universe. Now the end of the universe is the good of the intellect, i.e., truth. The
pursuit of wisdom in this sense is the most perfect, sublime, profitable, and delightful of pursuits.
All this is proved by appeal to the authority of "The Philosopher," i.e., Aristotle.
My purpose (he says) is to declare the truth which the Catholic Faith professes. But here I must
have recourse to natural reason, since the gentiles do not accept the authority of Scripture. Natural
reason, however, is deficient in the things of God; it can prove some parts of the faith, but not
others. It can prove the existence of God and the immortality of the soul, but not the Trinity, the
Incarnation, or the Last Judgement. Whatever is demonstrable is, so far as it goes, in accordance
with the Christian faith, and nothing in revelation is contrary to reason. But it is important to
separate the parts of the faith which can be proved by reason from those which cannot.
Accordingly, of the four books into which the Summa is divided, the first three make no appeal to
revelation, except to show that it is in accordance with conclusions reached by reason; only in the
fourth book are matters treated which cannot be known apart from revelation.
The first step is to prove the existence of God. Some think this unnecessary, since the existence of
God (they say) is self-evident. If we knew God's essence, this would be true, since (as is proved
later) in God, essence and existence are one. But we do not know His essence, except very
imperfectly. Wise men know more of his essence than do the ignorant, and angels know more than
either; but no creature knows enough of it to be able to deduce God's existence from His essence.
On this ground, the ontological argument is rejected.
It is important to remember that religious truth which can be proved can also be known by faith.
The proofs are difficult, and can only be understood by the learned; but faith is necessary also to
the ignorant, to the young, and to those who, from practical preoccupations, have not the leisure to
learn philosophy. For them, revelation suffices.
Some say that God is only knowable by faith. They argue that, if