The goal of Aquinas’ five ways was to prove the existence of God in conjunction with his faith in Catholicism. As both a Dominican friar and a philosopher, Aquinas aimed to combine his Catholic ideas with Aristotle’s proofs of the existence of a God. Aquinas’ proofs included five arguments that can be boiled down to the proof from motion, from efficient causation, from contingency, from the gradation in things, and the argument from design. Although Aquinas’ proofs are influential and were well received at the time, there are a number of weaknesses that deplete the strength of his argument for God.
Aquinas’ first argument is generally described as the argument from motion as it attempts to prove the existence of God from the motion of objects. The theory is derived from Aristotle’s claim that any change that effects an object is the result of an object going from having potential to change, to actualizing the change itself. With this view, nothing could change on its own, but rather, all objects must be changed through contact with another object that already has the characteristic. Such characteristics could be heat, as objects can only be hot or moving when interacting with something that was already hot, like a stove heating a pot. In this example, the pot has the potential to be hot, but cannot do so until it interacts with a already hot stove. This would then lead to a chain of objects changing each other from potential to actuality for infinity. However, to Aquinas, it could not be infinite, but rather there had to be a source at the beginning of time from which all characteristics originated from the same source, inferring a being with pure actuality. For Aquinas, the best explanation was the existence of an all-powerful God.
Aquinas’ second argument is best described as the proof from efficient cause, as it is derived from Aristotle’s notion of four causes: efficient, material, formal, and final. The argument mainly deals with the efficient cause, which refers to the thing or agent that brings about the creation of another object or being. For example, the efficient cause of a sculpture would be its respective sculptor, and the efficient cause of a piece of music would be its composer. Following almost the same line of logic as the first proof, the efficient cause of all things should lead back to infinity, however, Aquinas once again denies such a possibility and differs to his belief that there must be a single source of all efficient causes. Aquinas believes that there is nothing that can be proven to be the efficient cause of itself, as there is nothing that can create itself, however, he settles on the existence of an all-powerful God that brings all thing into being and had the ability to even bring themselves into being.
Both Aquinas’ first and second argument can be refuted in the same manner as they both follow the same line of logic. Aquinas’ argument of motion and efficient causes assumes that the infinite chain of efficient causes eventually points towards the existence of God, however we cannot be sure that God is the first source of change or efficient cause. The likelihood of the Big Bang being the first source of motion or efficient cause is just as likely as that of God, as neither the creation of God or the Big Bang has been discovered. It is also uncertain that there is only one single source of all change or efficient causes as there is no evidence that all change or creation is traced back to the same singular event or being. It can thus be elucidated, that any proof of God that follows this same logic of an infinite chain is not logically sound and must be reexamined or replaced.
The third proof is best described as that of the proof from contingency, as it refers to necessary and contingent objects. Necessary objects are objects that exist as a necessity of the universe, meaning that there is no world in which they don’t exist. Contingent objects all exist in dependence of necessary objects or other contingent objects and the universe would still exist if they ceased to exist. An example of contingent objects could be humans, as we could not survive without the existence of water, oxygen, or food. If these items did not exist, then humans could would cease to exist. It is also not unimaginable to see a world in which humans did not exist. Aquinas follows down the same chain as he did before, settling on the logic that if all objects were contingent, then there would be a time where nothing existed and thus nothing would still exist. He then traces back the origin of all things to existence of a single necessary object, and that being an all-powerful God, of which no universe would be imaginable without their existence and doing.
The third proof can be refuted using Reductio Ad Absurdum, which means that granting an assumption of an argument leads to absurdity, and thus the argument as a whole can be rejected. In Aquinas’ third proof, it would be absurd to assume that there was a time where there was nothing and thus everything should still be nothing, therefore the argument can be immediately refuted. There is also the critique of the timeline that Aquinas provides in the same statement, as it is not mutually exclusive that every object fails to exist and that they must all fail to exist at the same time, as there may be an overlap. Our modern theory of physics also rejects this proof, as the existence of matter and energy are to be believed to have always existed in the actual world, however, this may be proven wrong if given more evidence.
This then leads to the fourth proof, which can be described as the proof from the gradation in things, as it refers to the gradation or degree of certain characteristics in all beings and things. The argument stems from the Aristotelian notion that anything that has a characteristic such as heat, strength, intelligence, etc., has to receive the characteristic from something that is maximally hot, strong, or intelligent, etc. An example would be that of a hot pan, as a hot pan derives its heat from something much hotter, such as a stove or even a fire. Aquinas then sets up the argument to state that since everything derives its gradation from a maximally characterized item, it would make sense for there to be a maximum exemplar, that holds the maximal quantity of all characteristics. Aquinas then justifies this by using God as the all-powerful maximum exemplar.
This argument can be refuted by attacking the numerous assumptions that both Aristotle and Aquinas make. Firstly, the existence of a maximum exemplar does not seem to have any concrete evidence supporting it, as some characteristics may not have a maximum as they are subjective, such as comedy. Even if all characteristics did have a maximum exemplar, it is not certain that there only had to be one singular maximum exemplar for all characteristics, just as the critique for the first two proofs state. There is also the criticism that God would have contradictory features, as God would be both the hottest and the coldest at the same time. However, this can be responded to by stating that contradictory features are on the same gradation, as something with the coldest can be defined as something with the least heat.
Lastly, Aquinas utilizes an early version of the design argument in order to prove the existence of God. Aquinas agrees with Aristotle that all things designed to act for a purpose. Objects such as rain exist in order to water crops, which exist to feed humans. Ultimately, everything serves man, even if they are natural objects that don’t have minds. Aquinas then deduces that if natural objects such as rain does not have a mind, then something must be controlling them and giving it a purpose to fulfill. Aquinas argues that natural objects and processes must then be given a purpose and controlled by God, as he is all-powerful and is the only external power that could give purpose to something that cannot choose its own purpose, like humans can.
This can be refuted using the same logic as other proofs, as there is no reason that every natural object must be given purpose by the same mind, assumed to be the mind of God. This criticism also can only work when assuming that natural objects are given an actual purpose, which can also be debated, as processes such as rain can both worth for humanity’s gain, and its downfall through floods and heavy rainstorms which harm humans. Had the purpose been to aid humanity, this evidence would not follow the same logic.
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