Thomas Aquinas’ weakest argument is, without a doubt, the argument from gradation. In Aquinas’ fourth way, God is defined as the Absolute Being which, in a sense, is used as a yardstick for the measurement of all qualities.
There is a belief that some things are better than others, which can be applied to all things, but can it really be applied to everything? Is one rose better than another if equal in age and care? Who determines which one is better? If there were two identical twins, is one better than the other? Aquinas believed that things are good only in proportion to how closely they resemble that which he considers perfect. Therefore, if there is nothing that is perfect, there can be nothing that is good. But this is not necessarily true. Who defines perfection?
Isn’t the concept of perfection based upon the qualities and standard set by the perceiver? Is God viewed as perfect through the eyes of a Satanists? What if a Satanist’s view of perfection is directly opposite? Aquinas’ goes on to say that if anything is good, there must be something that is perfect, and with this in mind, Thomas Aquinas stated, “Therefore there must also be something which is to all beings the cause of their being, goodness, and every other perfection; and this we call God.” But once again, this is not necessarily true. Perfection is in the eye of the beholder.
Aquinas believed that all things in our experience must possess some degree of perfection in order to exist, but this is not true. Simply put, if there is a God that is absolutely 100% perfect, then one must accept that there is something else that is absolutely 100% imperfect. If this is true, then it has absolutely no degree of perfection which negates Aquinas’ belief. In addition, who measures the perfection of God? And if one agrees that the perfection of God cannot be measured, then one must accept that God does not exist.
Aquinas believed that all things that exist display gradations from greater to lesser perfection, but this is not true. Can fire have a gradation from greater to lesser perfection? Once again, who determines or defines what is great and what is not? And if Aquinas uses this to prove the existence of God, he is simultaneously proving the existence of something that is completely opposite of God, something completely not good, completely evil; Satan.
There is a gradation that we find among things from more to less and vice versa. Just as Aquinas believes that everything that exists possesses some degree of perfection, there must be a being that is the cause of the death, destruction, chaos, evil, and any other imperfection of creatures; Satan.
Simply put, this is the weakest argument of Thomas Aquinas’ Five Ways to prove the existence of God. It leaves to many openings for criticism and skepticism.