itic:
The foundation of both goal and correct means is called the natural law, which is knowable by human reason but open to rejection by the individual. There are four cardinal virtues, or optimum means, for use in every state of life: prudence, justice, fortitude, and temperance. The highest of all is prudence, which binds all virtues together and securely guides humanity to happiness.
Thomistic theology, which he calls sacred doctrine, is distinct from pure philosophy and depends on the divine gift of faith involving the whole realm of revelation, divine law, ecclesial worship, the spiritual life, and human speculation about these subjects. The realm of faith is strictly speaking "super-natural" in that its truths, values, and efficacy transcend the realm of "nature." Probably the most famous example of Aquinas' reliance on Aristotle can be seen in the First Way in which Aquinas uses Aristotle's notion of the unmoved mover to prove the existence of God. In Metaphysics Beta, Aristotle argued that change implies the existence of an ultimate and unchanging source of change, since an infinite regress of causation is impossible. According to Aristotle,
If there is nothing eternal, then there can be no becoming; for there must be something which undergoes the process of becoming, that is, that form which things come to be; and the last member of this series must be engenerated, for the series must start with something, since nothing can come from nothing.
When we examine Aquinas' First Way, the argument from motion, the similarities to the latter view become apparent.
Metaphysics for Aquinas is speculative wisdom, or natural theology. It is all about being-as-such and about the First Cause as the source of all being. The most "sublime truth" of this wisdom for Aquinas is the realization that all creatures are composed of a "nature" and a borrowed existence (esse), while God's nature alone is "to exist":
God is sub...