Is Faith Reasonable?

Is Faith Reasonable? February 5, 2023

Some wit once wrote that faith is believing something one knows isn’t true. Of course, this is not how the mind works, but it raises a question. In issues of faith, whether that is faith in one’s own abilities or a transcendent God, what constitutes evidence? Put differently, what is sufficient proof to persuade someone to have faith in God?

In this paper, I will explain what Catholicism means by faith. I will then examine the various forms of reasoning and what constitutes proof in matters religious.

What Is Faith?

Frequently faith is thought of as a synonym for trust. Indeed, faith and trust exist relationally. 

The Bible defines faith as “the realization of what is hoped for and evidence of things not seen.” (Hebrews 11:1). In a sense, faith means having a good reason to consent to a proposition. By comparison, trust is acting or relying upon that faith. For example, one may have faith in the existence of God (have reasons for accepting that He exists). Based upon that faith, one may trust that God will save him from his sins. This trust entails living in a certain way (e.g., being baptized, going to confession, and attending Mass). 

If faith, or at least well-developed faith, is having good reasons to believe in the truth of a proposition, what constitutes good reasons? That is to say, what evidence is necessary before one can accept something as a matter of faith? 

In order to address that question, it is necessary to understand human reasoning and what comprises proof.

Evidence And Reason 

What constitutes evidence frequently depends upon the discipline or area that incorporates the subject. Scientific evidence varies considerably from evidence allowed in legal proceedings, and both differ from what constitutes proof of historical events. And even legal proceedings will admit different types of evidence depending on the nature of the case. 

Complicating matters further is determining what reliable sources of evidence are. Generally, one places greater trust in evidence and arguments provided by experts than in less knowledgeable sources.

Evidence is entirely dependent upon the reasoning used. For the purpose of this article, it is useful to identify three categories of reasoning that lead to conclusions. They are deductive, inductive, and illative. 

Within the process of deductive reasoning, a proof is an accepted inference by which one comes to a conclusion. In a deductive argument, if the premises are true and the logic valid, the conclusion follows necessarily. If it is true that all men are mortal and that I am a man, it must be true that I am mortal. 

Conclusions that are drawn from induction do not rise to the level of certainty. If every cat one observes purrs, it is likely (but not certain) that all cats purr. 

Illative reasoning is a term coined by Cardinal John Henry Newman. It is quite similar to inductive reasoning. In illative reasoning, one makes judgments and draws conclusions based on circumstantial evidence and prior findings rather than on direct or empirical evidence. The illative sense moves from abstract concepts, for example, a concept about truth, to reasoning that there must be a concrete source of truth. 

Having reviewed matters of evidence and reason, I turn now to discuss the use of evidence and reason in matters of faith.

Why Believe? 

The object of one’s inquiry dictates the type of evidence one seeks, and the reasoning one utilizes in drawing a conclusion. For example, using the scientific method would be inadequate for understanding a historical event.

In the case of religious faith, one is claiming that there exists sufficient inferential evidence for the existence of God. Why inferential? Because if one could prove the existence of God with deductive certainty, one would not need faith; one would know. To paraphrase Saint Paul, we need faith on earth because we “See through a glass darkly.” In Heaven, we shall see face to face. In other words, there is no faith in Heaven; one “knows” God. 

What, then, is proof sufficient for a reasonable person to come to have faith in God? The level of proof necessary to convince differs from person to person. What is persuasive to one may not be persuasive to another. 

Yet it is necessary for an advance in knowledge to acknowledge a standard. Owing to the nature of faith, what constitutes evidence must be philosophical in nature and sufficient in quantity and quality that a reasonable person would infer the truth of the proposition in question. As such, proof in matters of religious faith is a series of inferential premises that lead to a probable conclusion.

The history of theology has seen numerous arguments appear in support of faith. For the sake of brevity, I will touch upon two sets of arguments that argue for the existence of God and make having faith reasonable.

The first is called Pascal’s Wager. Formulated by the French polymath Blaise Pascal, the wager is intended to utilize probability as an argument for faith. Pascal did not think it possible to settle the question of the existence of God entirely but thought that faith was quite reasonable.

The wager is formulated thusly: If God exists and one believes in God, one obtains Heaven (eternal happiness). If God exists and one does not believe, one may go to Hell (eternal damnation). If God does not exist and one believes, one neither gains nor loses anything. The same is true if one does not believe and God does not exist. Since one gains eternal happiness by having faith and loses nothing if God does not exist, it is prudent to have faith in God.

The second argument is actually a series of five independent arguments from Thomas Aquinas. They are appropriately called the Five Ways. I do not have space here to go into each argument. I will list the arguments and provide links to my article explaining them.

The Five Ways are an argument from motion (; an argument from efficient cause (; a cosmological argument (; an argument based on gradation (; and finally, the fifth way argues from the evidence of design (


Too often, faith is thought of as credulity or superstition. Yet faith is an essential part of the human experience. Whether that faith is in science, one’s spouse, or God, everyone believes something on faith. 

In this article, I have sought to address the question of whether faith is reasonable. The history of Catholic theology and western philosophy is replete with arguments and proofs that an open-minded (atheists are very dogmatic) and reasonable person would conclude that it is indeed very reasonable to believe.

I shall close with the words of our Savior, “Blessed are those who have not seen [Jesus] and have believed.” (John 20:29).

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