Third Meditation Proof for God’s Existence (AT 40-52)
1. Whatever exists must have an efficient cause or reason for its existence (41).
2. It is impossible that a nonexistent should cause an actual thing or an actual
perfection in anything (40).
3. Therefore, whatever reality is present in any existent must be present formally or
eminently in its efficient cause (40).
4. Therefore, whatever reality is present objectively in an idea must be present
formally or eminently in the efficient cause of the idea (41).
5. I have an idea of God, that is, of a wholly perfect, infinite and independent
substance (45).
6. I am not wholly perfect (45-46).
7. Therefore, infinite perfection is not present in me either formally or eminently
(46).
8. Therefore, I am not the cause of my idea of God (46).
9. Infinite perfection cannot be contained formally or eminently in any being except
an infinitely perfect being, that is, in God himself (50).
10. Therefore, the idea of God in me can have only God himself as its efficient cause
(50).
11. Therefore, God exists (51).
Replies to possible objections:
1. The idea of God is not perceived merely by negation of the finite. (45)
2. The idea of God cannot be materially false, like the idea of cold, which may represent
a privation as something positive. (46)
3. One of God’s perfections is supreme simplicity, which cannot be caused by an
aggregate of causes, since these lack that perfection. (50)