Saint Thomas Aquinas

1. Saint Thomas Aquinas Main Themes

2. Overview • Apex of Scholastic Philosophy • Expert on Aristotle • Blended Christianity with Aristotle • Like Augustine had blended Plato with Christianity

3. Metaphysics • There is one Truth • Truth has two sides • Natural truth • Based on sensory perception • Supernatural truth • Based on divine revelation • Human knowledge is insufficient to access this truth • This truth is also known as “mysteries” • Both sides of the one truth comprise the real world

4. Epistemology • Mysteries are not contrary to human reason • Reason can take one only so far • Example: Logic leads anyone to know that God exists and that there is only one God; but faith is needed to know God is Trinity and to relate to Him • Reason seeks to understand what faith believes • The real world does not deceive; only the mind deceives

5. Metaphysics • Matter remains constant throughout any change • Change can be explained using Aristotle • the efficient cause is that which produces the change • the material cause is the stuff that changes • the formal cause is the form the stuff takes • the final cause is what explains why there was a change • Form cannot exist apart from matter • Any separation of form and matter is simply mental

6. Metaphysics • Agrees with Aristotle on Substantia and Accidens • Essence = whatness • Characteristics = thisness (individuality) • Criticizes Aristotle for not defining existence

7. Essence vs. Existence Problem 1: Do sensory perceptions lead us to know that all things always exist? Problem 2: Do sensory perceptions lead us to know that everything exists only in one form?

8. Essence vs. Existence • Another way: What is the most important actuality in any thing? • Can something “be” without existing? What is the “beingness” of the idea? The human which may come from you? The tree which may grow in a few years from the acorn that will form next spring? • All these items are potential. This means that they have essence—within the thing that will produce them. They will become “actual.” But is that the same as existence?

9. Essence vs. Existence • Problem 3: Nothing can cause its own existence. • Whatever can cause its own existence would already need to exist (as cause) before it existed (as effect) • Example: The child receives its essence from the parents, but the child cannot conceive itself. Yet there is a child (potentially) in you that may become actual.

10. Essence vs. Existence • Solution: Essence does not guarantee existence • What something is (its essence) is not the same as that it is (its existence) • Therefore, we must distinguish not two things but three things: • What something is (substantia; essence) • It’s particularity (accidens; qualities) • And that it is (existere; existence)

11. Essence vs. Existence • Corollary: There is not only an Unmoved Mover. There is also an Uncaused Cause of Existence. • God is the perfect being that exists in himself yet is the source of the known universe • Only in God are essence and existence the same. • Therefore, God is not merely Pure Act (Aristotle) • God is Pure Act of Existence (Aquinas)

12. Essence vs. Existence • Formula • Aristotle • (m+f) = sub (e+a) • Aquinas • Ex = S (M+F) + A • Existence is substantia (or essence) actualized (in actuality)

13. Proving God’s Existence • Anselm’s ontological argument: • God’s existence is predicated upon my ability to think of a being that exceeds any being I have met • The most just, perfect, most knowledgeable, almighty, immortal being is God • Aquinas: God’s existence cannot be proved merely by considering the word God. • There are five ways to prove God’s existence.

14. Proving God’s Existence • First Way: Prime Mover • God is the Unmoved Mover • Second Way: Prime Existence • God is the Uncaused Cause of Existence

15. Proving God’s Existence • Third Way: Need-To-Exist • Most things in nature are such that it is possible for them not to exist. • They “need not exist.” • That which need not exist did not, at one time, exist. • Yet there must be existence of something the existence of which is necessary; and that necessary being has its own necessity.

16. Proving God’s Existence • Third Way Again: Contingency • All things are contingent • Contingent = dependent upon something else to maintain existence • Example: Humans depend on oxygen; therefore, humans are contingent • There must be something that is the source for all these contingent items • Since it is the source, that one thing is not contingent and is above contingency • Hence, it needs nothing else to exist

17. Proving God’s Existence • Fourth Way: Moral Argument • All things possess some degree of goodness, truth, nobility, beauty, or other virtues • There must be a source for all beauty, goodness, truth, etc., which all things possess • That “source” is beauty itself, truth itself, nobility itself, etc.

18. Proving God’s Existence • Fifth Way: Intelligent Design • All things in nature have a purpose or end • All things move from potential to actuality • Each thing functions according to its own particular purpose or end • Each thing functions according to its design or plan • No thing deviates from its plan • Acorns do not produce elephants • Therefore, there must be an intelligent being who originated the plan or design or purpose for each thing and all things

19. Proving God’s Existence These five ways demonstrate the existence of God These five ways demonstrate that God is one (monotheism) These five things do not demonstrate the existence of the Trinity or a personal deity

20. Proving God’s Existence • The first three arguments are cosmological • The fourth argument is moral • The fifth argument is teleological • None of these arguments are ontological • Aquinas uses his arguments against Anselm, who is the one that offers the ontological argument