According to Aquinas, no division exists between the “revealed” truth known by faith and the general, “natural” revelation known by reason; truth itself is a unity, because ultimately the same God authors all that is true. Grace does not destroy nature but rather perfects it; consequently, supernatural revelation certainly will go beyond natural revelation but will not contradict it. For example, one may know of God’s existence simply because the Bible declares it, but one may also know of God’s existence rationally by the Five Ways (motion, causality, contingency, degrees of perfection, and teleology). By reason, one may also know some of God’s attributes, such as his unity and perfection. However, some aspects of God, such as his Trinitarian nature, may be known only by faith.
Likewise, Aquinas says moral laws may be known directly by God’s commands but are also accessible to all by the “natural law” written in the human heart. God’s “eternal law” disposes all things by means of God’s perfect knowledge and will, and is therefore identical with what is meant by the theological term “providence.” Humans cannot, of course, know completely this eternal law, but what humans can grasp of it through their reason is the natural law. The human law (civil law, criminal law) should be based on the natural law; for example, criminal penalties for murder are based on the natural law prohibiting murder.
Human nature is a...
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