Saturday, April 23, 2016
Thomism is based on a system of metaphysics that Thomas Aquinas adapted from Aristotle. Aristotle posited the existence of act and potency as a means of explaining phenomena observed in the natural world. It was said that movement (which can be any of a variety of types of change) is explained as the actualization of a potency. Actualization was thought to be the fulfillment of an end or goal. Movement occurs when an object that has the property of potential with respect to a certain kind of actualization is acted upon by another object that has that actualization. Take, for example, a cold stone. It has the potential to become warm, and will do so when placed in contact with a hot stone. The movement (becoming warm) is the actualization of the potential (to become warm), and is caused by the hot stone (which is warm).
In keeping with this metaphysical system, God is said to be pure actualization (or act). God is the ultimate cause of all movement, but God himself is not moved by anything. The reason is that movement requires some potential that must be actualized. But God has no potential - he is pure act, he is perfectly fulfilled. But this belief leads to some problems, as we shall see.
In the real world, anything that moves or changes something else is itself moved or changed in the process. To realize this, note that the laws of physics absolutely require it. There is conservation of energy, which implies that energy being imparted to some object must be lost from something else. A hot stone is cooled when its heat is transferred to a cold stone. There is conservation of momentum, which implies that the movement of an object is balanced by the "equal and opposite reaction" of another object. In fact, any kind of caused change is the result mutual interaction between objects, and affects all of the involved objects. It is impossible for something that is completely immobile and immutable to cause any change at all in some other object. The idea of an unmoved mover is contradicted by the laws of physics.
One might argue that God isn't subject to the laws of physics. But what reason do we have to suppose that this kind of causation (pure act) exists at all? Aquinas claimed to be an empiricist, and that his explanation of the causes of motion are based on observation. He even claimed that belief in God can be based on a posteriori argument. Aquinas' Argument from Motion specifically claims to be based on the observation. It says: "Whatever is moved is moved by something else. Potentiality is only moved by actuality." But modern empirical observation tells us that motion is mutually caused. It is not the case that something causes motion without also being moved. So there is no empirical basis to conclude that there must be an unmoved mover, but there is good reason based in science to think that the idea of an unmoved mover is false.
Another aspect of modern physics that was unknown to Aristotle and Aquinas is the concept of inertia. To them, movement had to be sustained by a mover. Aristotle postulated a number of prime movers who were responsible for the rotation of the celestial spheres. Without their continuous efforts, that movement would stop. But science tells us that an object placed into motion will remain in motion as long as nothing else acts upon it. The idea that an object in motion must be continuously actualized raises the question: "actualized toward what end?" A planet in orbit around the sun can make billions of revolutions, and after all that, it is still in exactly the same state. What kind of actualization or fulfillment is that? It might make more sense to say that placing it in motion in the first place was the actualization, with the end being the achievement of orbit, but that would be a violation of the concept of movement. So the Thomist seems to be in a quandary. Either something is wrong with his concept of movement, or something is wrong with his concept of actualization.
Thermodynamics also refutes the idea of actualization, in the sense that the universe is destined by physics to end up in a state of "heat death". Heat death can best be described in terms of Thomistic metaphysics as the loss of all actuality. There is no form or function. But thermodynamics is not something that Aristotle or Aquinas knew about, and so they have no explanation for it. They defined movement as actualization, which is seen as the fulfillment of some end. God is pure act, and as such, he is completely fulfilled. The movement of the universe caused by God is seen as movement toward the kind of fulfillment that God provides. In the long run, the universe being moved by God must move toward an end that is actualized in God. But heat death is the opposite of that. It is the complete loss of actualization. The whole universe is in motion, to be sure. But is is moving away from actualization. Therefore, modern physics repudiates the idea that movement is actualization.
Thomistic metaphysics seems appealing to someone who wants to justify his belief in God. But don't think about it too much, because it will lead to contradictions. And while the Thomist might insist that it is completely compatible with science, he can only make that claim by ignoring the glaring inconsistencies between them. Thomists claim that their metaphysics is based on empirical observation, but science actually is based on empirical observation, and the two don't see eye to eye.