The Five Ways of Proving the Existence of God: A Thomistic Perspective

Posted on May 4, 2024 in Philosophy and ethics

Analysis of Ideas

a) Nothing moves unless it is moved by something else. This is because everything that moves is in potency to move, and something in act is required to actualize this potency.
b) It is not possible for something to be in potency and act with respect to the same thing. This is because potency and act are opposites, and something cannot be both opposite things at the same time.
c) Similarly, something cannot move and be moved by the same thing at the same time. This is because movement is a change from potency to act, and something cannot be both in potency and act at the same time.
d) Everything that moves needs to be moved by something else. This is because nothing can move itself, since movement is a change from potency to act, and something cannot be both in potency and act at the same time.

a) The starting point of the first way is the observation that everything that moves is moved by something else. This principle is based on the idea that movement is an act of a mobile being, and that every mobile being is in potency to move.
b) The second principle is that it is impossible to proceed to infinity in the series of movers. This is because if there were an infinite series of movers, then there would be no first mover, and without a first mover, there would be no movement at all.
c) The third principle is that everything that moves is moved by something else that is in act. This is because movement is a change from potency to act, and something cannot be moved from potency to act unless it is acted upon by something that is already in act.
d) The fourth principle is that it is impossible for something to be both a mover and a mobile with respect to the same movement. This is because movement is a change from potency to act, and something cannot be both in potency and act at the same time.

Plato used movement to prove not the existence of God but the existence of a soul in the cosmos.
Aristotle also used the notions of potency and act, and the two principles of the Thomistic proof: everything that moves must be moved by something else, and it is impossible to proceed to infinity in the series of movers.

Movement: Movement is the actualization of a potential being as such, or the passage from potency to act. Aristotle distinguishes two senses of movement: a broad sense, whereby movement would be all change, both substantial and accidental, and a strict sense, according to which only local change would be movement, that is, quantitative change.
Power: Aristotle conceived power as a mode of being between nonbeing and being in act. Being is potentially able to become something; act is what has become something after change.
Motor: A motor is that which moves something. In order to move something, a motor needs to be in act with respect to that which it moves.
God: For St. Thomas, God is the same as being itself subsisting, and in God, essence and existence are identified. Unlike creatures, God is simple, perfect, infinite, and necessary.