Religion of the Spirits
In responding to adherents of the Religion of the Spirits, one might expect very different statements by St. Thomas Aquinas and the philosopher Friedrich Nietzsche. Indeed, these two personalities are opposite ends of the religious scale, with the former believing without any doubt that God exists and Catholicism is the true religion, and the latter being a believer in nihilism, physical life as the only existence that can reasonably be expected, and the non-existence of God. One similarity between Aquinas and Nietzsche is that they both believe unshakably in their respective viewpoints. There is therefore not much likelihood that the Religion of the Spirits will be able to convince either of their "truth."
If believers in the Religion of the Spirits were therefore to try and convince Thomas Aquinas of the truth of their religion, I believe he would in turn explain to them that there is only one truth, which is not the world as they see it. Within Aquinas' global concept of "truth," I believe he would isolate two separate issues to discuss with the Spirit believers: the first is that any sort of spirit worship is religiously and morally questionable, as the only entity to legitimately worship is God himself. Because the most likely response to this is that there is no God, the next discussion would focus on Aquinas' reasons for believing that there is a God.
To be more specific, Aquinas would begin by explaining his concept of biblical truth. Specifically, he would counter the Spirit believers' worship of the spirits by...
He would explain that God is the only entity to be worshiped, and that he demands to be worshiped in a certain way. At the same time, he would explain that only God has the power to give blessings or take them away. To connect with the belief system of the Spirit believers, Aquinas might go on to explain that their "good" spirits should in fact be replaced by God and their "bad" spirits by Satan.
When attempting to argue that God does not exist, I believe Aquinas would counter with his reasons for believing that God does exist. In the context, his strongest arguments for the existence of God would be the nature of cause and effect and the order of the world and everything in it according to an apparently higher plan.
Aquinas refers to the rule of cause and effect the nature of the "efficient cause." His argument here would be that there is a chain of causes to bring everything into existence. Aquinas divides these causes and effects into three stages each: the first cause, the effect of this cause (the middle), which becomes a further cause for another effect, which could become another middle, or the final effect. According to Aquinas' reasoning, there has to be a first or "efficient" cause for there to be any effects at all. Because the world as we know it exists, there has to be an efficient cause, which his God.
Second, Aquinas would use the laws of nature and the rules of the universe to explain his belief in God. The human body itself, as well, operates according to rules and…
