Many philosophers and theologians have provided varying arguments for the existence of God. These arguments are either a priori, understood independent of worldly experience and observation (Ontological Argument), or a posteriori, dependent on experience and based on observations of how the world is (Cosmological and Teleological Arguments). This paper will focus on the Cosmological Argument, and show that its underlying principle, the Principle of Sufficient Reason, fails to establish it as a sound argument for the existence of God. To accomplish this, I will, first, define the Cosmological Argument and the Principle of Sufficient Reason; then explain the argument, and how it is based on the Principle of Sufficient Reason; and finally, show that there is not enough evidence to prove that the Principle of Sufficient Reason is true, which in turn leads to the flaw in the Cosmological Argument.
First, what are the Cosmological Argument and the Principle of Sufficient Reason? There are many versions of the argument. Saint Thomas Aquinas (in the thirteenth century) and Samuel Clarke (in the eighteenth century) are the dominant contributors in the development of the argument (Rowe 21). Though their arguments differ slightly, both men based their arguments on the observation that the world is rooted on causal relationships. Their arguments can be summarized into one argument as follows:
(1) Either the world is made up of things that depend
on others for their existence (dependent beings), or things that are self-existent (independent beings).
(2) Not everything can depend on another for its existence.
(3) Therefore, there is some self-existing being, and that being is God.
The Principle of Sufficient Reason (PSR) maintains that there must be an explanation (a) of the existence of any being, and (b) of any positive fact whatever (Rowe 24). Thus, there is an explanation for why I exist (PSRa), and also an explanation for every feature of my life (PSRb).
Second, what is the meaning of the argument and how is it based on PSR? Premise (1) stems from Anselm’s division of beings into the three cases: ‘explained by another [dependent beings],”explained by nothing,”and explained by itself [independent/self-existing being]’ (Rowe 22). The first rule of PSR holds that every being must have an explanation for its existence. A being that is explained by nothing violates this first rule, and as a result, is left out of premise (1). This allows for only two possible types of beings — either dependent or self-existent. If you hold PSR to be true, them premise (1) is uncontroversial. Because it is an either, or statement, only one of the two types of beings needs to exist for the premise to be true. We know that there are at least dependent beings, so premise (1) is true. Premise (2) states that everything cannot be a dependent being. Why is this the case? William Rowe does an excellent job of explaining why if PSR is true, then premise (2) is also true. He (Rowe 24-25) says let’s suppose that there has never been a self-existing being, but only an infinite series of dependent beings. In this series, every being has an explanation, because it is explained by the being that came before it and that caused its existence (follows with PSRa), but what caused the series? PSRb says that the fact that the series exists requires it to have an explanation, but if there have only existed dependent beings, the series will not have an explanation. It won’t do to say that As [where As equal dependent beings] have always been producing other As — we can’t explain why there have always been As by saying that there have always been As (Rowe 25). Thus, a self-existing being is the only explanation for the series, and premise (2) is true. Thus, because premise (1) shows that there are only two kinds of beings (dependent or self-existent), and everything cannot be a dependent being, it follows that there must be some self-existing being.
So far, it seems that the Cosmological Argument indeed proves the existence of a self-existing being. Both of its premises have been shown to be true, so it passes the premise test, and also, the conclusion follows from the premises — it passes the inference test. But has anything been overlooked? Yes, it has. The only way that premise (1) and (2) can be true is if the Principle of Sufficient Reason is also true. The question, of course, is whether or not PSR is true. What reasons for its truth could we offer? Rowe suggests two traditional reasons offered in favor of accepting the truth of PSR. The first reason is that some have held that PSR is (or can be) known intuitively to be true (Rowe 29). Just as we know that two plus two equals four is true, the defender of PSR claims that the same sort of thing is true about PSR. Once PSR is understood, the understanding in itself reveals that it is true and must be true. The problem with the first defense of PSR is that while everyone who understands 2+2 knows that it does and must equal 4, very few people who reflect on PSR find that it must be true, and some even claim that the principle is false (Rowe 29). Why couldn’t the world be such that there were things and positive facts that had no explanation? The second reason traditionally offered for defending PSR is by claiming that although it is not known to be true, it is, nevertheless, a presupposition of reason, a basic assumption that rational people make (Rowe 29). The defender of PSR suggests that all of us presuppose that PSR is true, and that we couldn’t engage in our everyday activity if we took seriously the possibility that it might be false. The problem with this second defense of PSR is that it even if it were true that we all presuppose PSR to be true, that wouldn’t show that it was true. Even if PSR is a presupposition we all share, the premises of the Cosmological Argument could still be false. For PSR itself could be false (Rowe 29).
Ultimately, if we want to use the Cosmological Argument to prove the existence of God, then we need more evidence to prove that the Principle of Sufficient Reason is true. PSR is the basis for the premises of the Cosmological Argument, and Rowe has shown that the traditional arguments in favor of the truth of PSR are unsound. Until there is evidence to prove that PSR is true, the Cosmological Argument is not able to provide support for the existence of God.