Aquinas and the Existence of God

According to Aquinas, God’s existence ‘can be proved in five ways’ (Summa 1.2.3).
From the way in which he presents the first, it seems that he prefers it (‘the first and the most manifest way is…’ Summa 1.2.3). This first way is an ‘argument from motion.’ ‘Whatever is in motion is put in motion by another’ (Summa 1.2.3). This necessity of ‘another,’ and so on, cannot go on to infinity. ‘There would be no first mover, and no other mover’ (Summa 1.2.3). That is why, the first mover is a necessity. This first mover is ‘put in motion by no other’ (Summa 1.2.3). And this is God.
The ‘second way’ is an argument ‘from the efficient cause’ (Summa 1.2.3). We do not know a thing to be ‘the efficient cause of itself’ (Summa 1.2.3). All efficient causes come in order (first/intermediate/ultimate). The cause and effect go together; if we take the cause out, we take away the effect. So we have to admit a first efficient cause (Moore 2011, 401); and that is God.
The ‘third way’ is an argument from ‘possibility and necessity’ (Summa 1.2.3). Things are possible to be and not to be. At one time nothing existed (Moore 2011, 401), and ’it would have been impossible for anything to have begun to exist’ (Summa 1.2.3). ’That which does not exist only begins to exist by something already existing’ (Summa 1.2.3). That is why, ‘there must exist something the existence of which is necessary’ (Summa 1.2.3). This being has of itself its own necessity, and causes in others their necessity (Summa 1.2.3). And this is God.
The ‘fourth way’ is an argument based on ‘the gradation to be found in things’ (Summa 1.2.3). They resemble in their different ways ‘something which is maximum’ (Summa 1.2.3). Because there is something which is truest, noblest, there is ‘something which is uttermost being’ (Summa 1.2.3). ‘The maximum in any genus is the cause of all in that genus’ (Summa 1.2.3). That is why, there must be something which is ‘to all beings the cause of their beings, goodness, and every other perfection;’ (Summa 1.2.3) and this is God.
The ‘fifth way’ is an argument based on ‘governance of the world’ (Summa 1.2.3). The natural things which lack in intelligence, act for an end. They cannot ‘move towards an end, unless it be directed by some being endowed with knowledge and intelligence’ (Summa 1.2.3). And this is God.

Bibliography
Aquinas, Thomas. Summa Theologica. Vol 1 - The First Part. Albany: Books for the Ages, 1997.
Moore, Brooke Noel. and Bruder, Kenneth. Philosophy, The Power of Ideas. 8th ed. New York, McGraw Hill, 2011.
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