Before we discuss the strengths and weaknesses of Thomas Aquinas’ Cosmological Argument, it is necessary to outline his logic. Aquinas argues for the existence of God based on observable truths that are evident in nature. These truths are the fact that some things are in motion, that things are caused, that it is possible for things either to or not to exist, that things have different degrees of certain properties or perfections, and that natural objects always act for some end.
First, we will consider his observation that things are in motion and that things are caused. Aquinas argues that if something is caused or moved, we have to find out what caused that, and what caused that, etc. on to infinity. He reasons that we must eventually arrive at a first mover or a first efficient cause, “and this everyone understands to be God” (Aquinas 98). We must also consider the prevalence of laws of nature, e.g. natural, non-living objects consistently acting to some end. Aquinas reasons, then, that it is clear that “they achieve their end, not fortuitously, but designedly” (Aquinas 99). Thus, there must be some intelligent being that directs everything to its natural end.
These arguments boast of several strengths. The foremost being that the argument is based on empirical evidence and observations. The laws of physics not only tell us that things cannot simply happen without any cause, but they also testify to the fact that there is an implicit design underlying all of reality. Aquinas capitalizes on the laws of cause and effect to explain why it is then necessary that there be some first efficient cause or first mover.
Furthermore, Aquinas’ argument addresses one of the most commonly asked questions in response to the first two facets of his argument: “If God created everything, then who created God?” Aquinas observes that it is possible for something to either exist or to not exist. This fact demonstrates that there must be something which has a necessary existence otherwise, nothing would exist because there would be no first cause and no first mover. Not to mention, the question contradicts the concept of infinity and therefore makes itself inapplicable.
Despite these strengths, Aquinas’ argument is far from perfect. Aquinas notes that causes and effects cannot go on infinitely. At first glance, this seems to be an entirely reasonable claim. However, it is not airtight. After all, if we can suppose that God is infinite, can’t we suppose that cause and effect is infinite, or even that time is infinite? Aquinas’ argument is dependent on the linearity of time; however, if time were cyclical, this would blast a hole in the very foundation of Aquinas’ argument.
Another weakness of his argument is when he continually uses phrases like, “and this everyone understands to be God.” It is important to recognize that just because many believe that God has always existed and is the creator of the universe, this proves nothing about the actual first cause, first mover, or designer. The first efficient cause could just as easily have been an infinitely dense particle; the designer could have been a higher being that created us in an electronic simulation, etc. So even if we concede that Aquinas’ argument proves the existence of a first mover or a creator, he does not prove that this being is God.
Overall, Aquinas makes a robust argument for the existence of God; however, his case by no means proves the existence of God, nor is it likely to convince anyone of his point of view.
