Aquinas and Descartes 79possible in order to judge the truth or falsehood of each part.
3) Deduce from those few truths the implications that follow
in an orderly and logical fashion, moving from the simple to the
more complex.
4) Finally, keep records that are accurate and review the
logical order carefully so that the accuracy of the result will be
unquestionable.
This logical process must begin with self-evident truths,
premises which cannot be denied. The mental operation by
which these truths are established is referred to by Descartes as
“intuition.” Descartes defines intuitions as innate ideas per
ceived by the mind without any sense-involvement whatever.
These innate ideas are in man at birth. Mathematical axioms are
examples, as well as the idea of the soul, the idea of God, the
concept that nothing comes from nothing (ex nihilo nihil fit), and
the Aristotlean idea that a thing cannot both exist and not exist
at the same time. The careful application of the mind’s intuitive
knowledge followed by steps two, three, and four will enable one
to seek and find truth.
The mental process which led Descartes to his first and most
important premise, however, is that of methodical doubt. Every
thing must be looked upon with doubt, at first, in order to make
the operations of intuition possible. When one doubts everything
in the universe, no matter how obviously true it may seem, the
only reality which is accepted initially is the reality of the act of
doubting. Doubting, reasons Descartes, implies a doubter, an
entity which is giving the act existence. Since he defines doubt
ing and all other mental processes as “thinking,” he accepts as his
initial and guiding self-evident truth, “Cogito Ergo Sum”— I
think, therefore, I am.
This concept gives his entire philosophy its justification. He
proves, not only his own existence, but the existence of God, and
in turn uses the existence of God to prove the reality of the
material world. Of three basic proofs for the existence of God,
one deals with innate ideas. He claims that a finite being could
not create the innate idea of an infinite being, thus the infinite
being, God, must exist. “I should not, however, have the idea of
an infinite substance, seeing 1 am a finite being, unless it were
given me by some substance in reality, infinite.”
This infinite substance, God, is “A thing which exists in such