Can We Know God Exists?

Two of the most important questions that any human being can possibly ask are also among the most formidable and controversial in history: Does God exist, and can we know it? A firm answer in the affirmative or negative is decisive to the entire course of a life.

The first thing that must be distinguished is the way in which one can know God exists. There are two ways we can know this: either a priori, that is, from self-evident principles like the law of non-contradiction, or a posteriori, from sensations, experiences, and thoughts which do not come from within us like logic, but rather to us through living and observing.

The a priori proofs for God’s existence are oftentimes controversial and seem not to appeal to everyone. Many schools of theistic thought, such as Thomism, set them aside because atheism’s prevalence indicates that people can deny the existence of God without falling into any obvious logical error.

What this means is that if man can know that God exists, he cannot know it like he knows mathematical principles. This does not at all mean, however, that there is no way to know for certain; the second category of proof still remains. After all, in our daily lives, very few of our key questions are ever decided deductively, but we instead rely on our common sense and experience for answers.

A posteriori ways to know that God exists employ commonsensical and experienced-based methods to arrive at an answer. They’re quite innumerable, coming in as many different shapes and forms as there are experiences in peoples’ lives. The best known are Thomas Aquinas’s Five Ways, which BC students encounter in some form in Perspectives I or Philosophy of the Person.

Aquinas’s a posteriori proofs all rely on observations about the nature of the universe, especially chains of causes, the human instinct to reach for an absolute and objective way to measure goodness, and the sense of purpose and design that many things possess.

For example, Aquinas notes that all things have an apparent cause beyond themselves. However, an infinite chain of causes would exclude the possibility of a first cause to even begin the chain. Consequently, there must be some uncaused cause at the beginning of a finite chain of cause and effect. To deny this is to sink into the irrationality of admitting an infinite regress, which is repugnant to intelligence. 

It is up to any reader to assess such proofs and ponder whether they successfully connect common experience with the proposed answer. The proponents of these proofs say that they are perfectly reasonable to any disinterested observer. However, the a posteriori proofs, which provide affirmative answers to both questions, have some nuances.

Most theologians and philosophers are quick to concede that their arguments do not demonstrate everything about God. They claim to show that God is, but not what God is in specific terms. These proofs will not lead to distinctly Christian theology, but only to what is called natural theology, the knowledge that there is some deity with certain qualities like omnipotence.

In short, it’s evident that answering the question of whether we can know that God exists only leads to more questions. Humans are naturally drawn to understanding something as much as possible, even perfectly. To drop the line of inquiry at the first question is unfaithful to the desire for truth, the very same urge which impels the higher sciences and physics. Like a cause-and-effect chain—like a line of dominos—answering this fundamental question is only the very beginning of a broader inquiry.

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