by David De Paz
Around 800 years ago, the intellectual landscape in Europe and the Middle East was undergoing significant changes. With Christianity and Islam being dominant forces, the greatest intellectual minds were the scholars and theologians. However, this intellectual change would be further influenced by the rediscovery of Ancient Greek and Roman philosophy, particularly the works of Aristotle, which had a profound effect on the theological landscape. First, his work was translated into Arabic and used by Islamic scholars and theologians such as Avicenna and Averroes. However, in the 13th century, Christian theologians began to incorporate his philosophy into their own religion. The most notable of these was Thomas Aquinas, a doctor of the Catholic Church, an apologist, and a philosopher. Aquinas advocated for an approach to Christianity that combined faith and reason, using his knowledge of Aristotelian philosophy to articulate the truths of Christianity. In his most important work, Summa Theologica, he wrote about the Five Ways, or proofs, of God’s existence. Although amazing scientific and philosophical advancements have been made in the 800 years since the time of Aquinas, his Five Ways still apply to the modern world, especially in their modern forms to adjust to the knowledge that the human race has accumulated. The first three of the Five Ways are cosmological arguments, meaning they deal with the origin of the universe.
Taking inspiration from Aristotle, the First Way is known as the Argument From Motion. The argument can be articulated very simply: Everything that is in motion was caused to move by something else; either this chain is infinite, which would be logically incoherent, or there is a first unmoved mover. This unmoved mover is known as God. However, this basic explanation doesn’t do the argument justice, and often opens up the door to critics and questions which shouldn’t normally be a problem. Instead of the Argument From Motion, I believe it’s better articulated as the argument from change. This would fit more with Aquinas’ reasoning behind the argument, which is rooted in the principles of potentiality and actuality. He argues that change in one thing is caused by a different, actual thing acting upon its potential. A common analogy used is a melting ice cube. The ice cube’s potential of melting is being actualized by the warm air around it, but the air’s potential of being warm is being actualized by the heat from the sun, and the sun's potential of being hot is actualized by nuclear fusion in its core. This chain cannot be infinite, and so there must be a being which has no potential and is “pure actuality,” which Aquinas and Aristotle recognized as God.
The Second and Third Ways follow very similar logic; the former being the Argument From Causality and the latter being the Argument From Contingency. The Second Way asserts that everything that exists has a cause or reason for its existence, because things don’t just pop into existence without a cause or reason, which we can verify from our experience of this not happening in the world. The Third Way asserts that everything that exists could have failed to exist, and it was only caused to exist by something else. For example, a child would not exist without his or her parents. However, this also applies to the parents, and their parents, and everything in existence. Both of these arguments claim that everything in reality is contingent on something before it which either causes its existence or creates the conditions for it to exist, essentially “borrowing” its existence from something else. However, when using this logic retrospectively, this implies that there are three possibilities. One, this chain goes infinitely back, which is logically incoherent because it fails to explain why the chain ever existed in the first place. Two, if you go far back enough, at one time, nothing existed, but this implies that nothing could ever exist at all, because something cannot come from nothing. Therefore, the only plausible explanation for reality is an uncaused, self-existing being, which does not receive its existence from anything else; a necessary being, which we recognize as God.
These arguments are founded upon the Principle of Sufficient Reason (PSR), the widely accepted philosophical idea that everything that exists must have some sort of explanation for its existence. However, over the years, many philosophers have challenged this principle. Notably, David Hume and Immanuel Kant were both skeptical of it. Hume argued that our belief in causation is just a psychological habit that humans have based on experience, not a necessary feature of reality. However, this position is not verifiable, and also extremely controversial, as abandoning the Principle of Sufficient Reason would abandon the basis for any scientific reasoning. This intellectual nihilism would mean that anything at all could be arbitrary. However, empirical science itself refutes Hume, as it has continually reinforced the PSR through experimentation. Kant’s argument is more nuanced. He argued that the PSR is a mental structure, similar to Hume, but rather than argue for intellectual nihilism, he distinguished between the “phenomenal” world, or the world as we experience it, and the “noumenal” world, or the world as it exists independently of human perception. Kant argues that the PSR is limited to the phenomenal world, and that questions such as “Why does something exist rather than nothing,” are beyond human cognition. While this critique is not as controversial as Hume’s, it can be seen as self-defeating. The claim that reason is confined to the phenomenal world is a metaphysical claim in itself, meaning according to his reasoning, he can’t possibly know if this is true either. If reason is truly limited, then we cannot make such claims, as we would be overstepping our epistemological limits.
Others have attempted to counter the cosmological arguments by saying that the chain stops at either the universe or scientific laws. In other words, the universe and the laws that govern it are “brute facts” that are necessarily existing. However, there are two fundamental problems with this argument. First of all, the argument completely violates the Principle of Sufficient Reason because the universe and its laws do not explain their own existence, they would just simply “exist” without a cause or reason. Secondly, both the universe and its laws seem to be contingent, meaning that they could have ceased to exist or been different. Something with the potential to change like the universe or its laws needs something else which is actual to realize that potential. Therefore, their existence inherently points to an underlying cause or creator.
However, this might raise the question of why God, as the ultimate cause, doesn’t need a creator Himself. Classical theism answers this question by defining God as the necessary being whose existence is inseparable from His essence. If you told someone with no knowledge of the Earth about the essence of three animals: a lion, a unicorn, and a whale, would they be able to tell which one is not real? The answer is no, because everything’s existence, or whether it exists or not, is distinct from its essence, or what that thing is. However, using the same logic from the cosmological arguments, the essence of something is only caused to exist by something else, but God is recognized as the self-existing first cause. This means that God’s existence would have to be inseparable from his essence because he does not get his existence from anything else. This is why we say God is a self-explaining being, because existence is part of his very nature. The same does not apply to the universe or its laws, which is why we call them contingent.
Additionally, some people claim that quantum mechanics refutes the Principle of Sufficient Reason. This is because in quantum mechanics, particularly the Copenhagen interpretation, events can occur “without a cause,” which would challenge the idea that everything has sufficient reason. However, this is a misrepresentation of the principle itself. Quantum mechanics does not refute the PSR itself; rather, it challenges the idea of classical determinism, the idea that the universe’s state at any time determines its past and future. While this challenges the classical notion of causality, even if quantum mechanics are probabilistic, the probability distribution is still determined by quantum laws, meaning there is still a rational structure underlying these events. They are not truly without reason. The PSR is the foundation of all rational inquiry, and reason should not be sacrificed just to deny the existence of God.
In conclusion, while the cosmological arguments are not inherently verifiable, they are necessarily true under the Principle of Sufficient Reason, which is the foundation for all rational inquiry and scientific reasoning. Even 800 years ago, Aquinas was able to articulate these truths which have withstood the test of time, science, and philosophy.
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