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Philosopher inductees for the Cambridge University Hall of Fame, Cambridge, England.
J. G. MillerJune 20, 202310 min read

Can Philosophy Provide Evidence for God’s Existence?

This article demonstrates that philosophical reasoning can not only establish the existence of God, it can also illuminate some of God’s attributes (e.g., oneness, simplicity). 

In this article, four points will be accessed to prove that philosophy can provide evidence for God's existence:

  1. The logical necessity for the existence of an uncaused being (existing through itself) which is the cause of everything else that exists.
  2. The uncaused being must be absolutely unrestricted and utterly simple.
  3. There can only be one unrestricted being.
  4. Ascertain if philosophy can discern any more attributes of this one, uncaused, and unrestricted being.

Before beginning, there must be an understanding of the criteria for establishing the reasonableness of an argument.

A claim or proposition may be considered reasonable if it meets at least one of the following criteria (see the end of this article for a definition of the following terms): 

  1.     It can be affirmed by rigorous public corroboration
  2.     Its denial leads to a contradiction of publicly corroborated fact
  3.     Its denial leads to an intrinsic contradiction

Metaphysical Evidence for God's Existence 

Now we will begin presenting metaphysical proof for God’s existence. Because this is a purely logical argument, its reasonableness will rely on the third criterion, namely that denying it will lead to an intrinsic contradiction. A metaphysical proof starts with the nature of reality or the totality of being and, from this vantage point, deduces certain logical arguments.

There must be at least one uncaused being that exists through itself and is the cause for all caused beings.

If there were not at least one uncaused cause in the whole of reality (i.e., everything that exists), then the whole of reality would be constituted by only caused beings—that is, beings that require a cause in order for them to exist. This would mean that there would need to be something beyond the whole of reality that caused (or is causing) everything to exist. Without such a cause, there would be nothing in existence.

But how can there be something beyond the whole of reality if the whole of reality equals everything?

That is like saying, “I ate the whole pie, but fortunately, I saved you a piece!” Denying that there is an uncaused being within the whole of reality is an intrinsic contradiction. Therefore, there must be at least one uncaused being in the whole of reality, and, as indicated above, this uncaused being must be the direct or indirect cause for all caused beings.

The Question of the Infinite Regress of Caused Beings

One question that frequently comes up in these types of discussions is: “Can one arrive at a sufficient explanation for a particular being by postulating an infinite regress of caused beings?”

The reason that this approach will not work is because the insufficiency of the causes in the series is not quantitative in nature but qualitative. If the insufficiency was quantitative, then the addition of insufficiencies might make a sufficiency (e.g., twenty horses could pull what two could not). But the insufficiency in the series is not quantitative but qualitative.

Furthermore, two parallel mirrors will create an infinite series of images only if there is some “unmirrored” source image that is the cause of the mirrored images. The infinite series of mirrored images (caused by the mirrors) depends upon an original image (one not caused by the mirrors) for their existence.

Thus, even an infinite number of insufficiencies does not equal sufficiency. Therefore, one cannot get a sufficient explanation for a being’s existence by postulating an infinite number of insufficient causes.

Absolute Simplicity in the Evidence for God's Existence 

The uncaused being must be absolutely unrestricted and utterly simple:

  • Boundaries/restrictions are limiting and exclusive
  • Fewer boundaries/restrictions and more inclusion equal greater simplicity
  • What would absolute simplicity be like?

Boundaries/Restrictions Are Limiting and Exclusive

If something has the boundaries of a square, it cannot have the boundaries of a circle or a triangle in the same respect at the same time and in the same place. For millennia, philosophers have recognized that having fewer boundaries or restrictions allows for the unification of seemingly disparate realities.

An example from physics is the concept of a field. The properties of electricity differ from those of magnetism but are unified in the relatively less-restricted electromagnetic field. Space and time are very different realities that become unified in a gravitational or space-time field. The implication here is that fields, which have fewer boundaries/restrictions and are thus more inclusive, can unify lower orders of being without being subjugated to the boundaries of the things that they unify.

Fewer Boundaries/Restrictions and More Inclusion Equal Greater Simplicity

Take how the principle of simplicity as espoused by Greek philosophers like Thales, who proposed water as the absolutely simple element from which all other matter is composed. For Thales, Parmenides, Plato, and Aristotle, the simpler a reality is, the fewer intrinsic and/or extrinsic boundaries it has. As we have just seen, boundaries exclude. Hence, greater simplicity means fewer intrinsic and extrinsic boundaries, which entails less exclusion within itself and with other beings, which further entails a greater possibility for interaction and interrelationship with other realities.

What Would Absolute Simplicity Be Like?

Thus far, we have discovered an important metaphysical principle: the less exclusive and more compatible a thing is, the fewer restrictions or boundaries it has to limit its mode of being—or, as the aforementioned philosophers would put it, the simpler it is. If we take this concept to its logical end, an absolutely simple being would have no boundaries or restrictions. 

In other words, it would not be restricted to existing in this way or that way; nor be restricted to existing here instead of there, nor be restricted to existing now instead of then, but simply be. Furthermore, it would be able to unify all other being within itself because it would have no restrictions to give rise to exclusion or incompatibility.

The Simplicity of the Creator as Evidence for God's Existence

Now that we have looked at the arguments for an uncaused being and absolute simplicity, we are in a position to ask the question, “Is this uncaused being absolutely simple?”

Two Key Principles: Existence and Essence

The question of whether an uncaused being is absolutely simple is really a question of whether or not an uncaused being can have restrictions.

Recall that an uncaused being exists through itself. The proof that an uncaused being must be absolutely simple is centered on the following fundamental Thomistic principles:

  1. Existence: The act of being
  2. Essence: A particular way of existing (e.g., existing as a horse, a rock, or a proton)

According to Aquinas, all created (i.e., caused) beings are composed of both essence and existence. Thus, every real created being is a composition of “what it is” and “its act of existing.” It is the essence that limits something to a specific type of being (e.g., a horse). It is the act of existing that makes something real as opposed to imagined. 

Thomas deduced that these limited real beings must have their source in simple or pure existence—that is, existence not restricted or bounded by essence. He referred to this pure being as “being in itself.”

He recognizes pure being as not only unrestricted but uncaused because it constitutes the ground of all other beings. Thus, if it had a cause, that cause would need to come from outside of all being—a logical contradiction in terms. This purely simple being is the cause of all caused beings, and because it has no restrictions or boundaries, it is able to unify all lower orders of reality.

Could There Be More than One Unrestricted Being?

This brings up a frequently asked question: “Why does Thomas Aquinas believe that there is only one simple and uncaused being? Couldn’t there be two or even more?”

His position is based on the following premises:

  1. If there are multiple uncaused beings, there must be a difference between those beings. If they are identical in all respects, then they are one.
  2. If there are differences, then at least one of those beings must be restricted (i.e., limited by essence and thus not absolutely simple). But given that there can be no restrictions on “pure being,” there must be only one unrestricted being.

Can Philosophy Provide Evidence for God’s Existence?

Thus far, we have used philosophical inquiry to discover that there must be one absolutely simple, uncaused being that is the cause of all other beings. Can philosophy tell us anything more about this uncaused being: can we really call it God? 

Thomas Aquinas, after using philosophical terms to describe God, sometimes closes his argument with the expression, “And this we call God.” 

Here we will follow his lead and acknowledge that the one absolutely simple, uncaused being that is the cause of all other beings is, in fact, God. Are there any other attributes of God that can be known through philosophy? The following is a list of divine attributes that philosophers have associated with God. 

God is:

  • Personal
  • Supremely Good
  • Omniscient
  • Omnipotent
  • Omnipresent
  • Eternal
  • Immaterial
  • Transcendent and Immanent

Although each of these can be logically derived, their proofs are less rigorous than what we’ve seen with the proofs in this post. Furthermore, some give rise to seemingly insurmountable problems. (For more information from Fr. Spitzer on philosophical discussions, see free will v. God’s omniscience and suffering v. God’s omnipotence.)

Because many philosophers see no way to get beyond the stripped-down description of God as merely a creator deity, this depiction of God has come to be known as the “God of the Philosophers.” The challenge for Christian philosophy is to show the seamless complementarity between the philosophers’ God and the personal, loving God of Christian revelation

For Thomas Aquinas, proof of the Divine attributes is rooted in God’s perfection. For whatever a creature possesses in a partial and imperfect way, God, as the source of all Being, must possess in a complete and perfect way.

For more evidence for God through Philosophy, see Father Spitzer’s article on metaphysical arguments for God’s existence and nature. 

*Definition of Terms

Rigorous public corroboration (1): that which is sufficient to make a preponderance of reasonable people believe that an affirmation of the claim is far more reasonable than a denial of it. Take, for example, the claim that Father Spitzer is currently in his office. This corroboration could occur through agreement from multiple persons witnessing Father’s presence in his office. In science, rigorous corroboration could occur through different kinds of experimentation, repetitions of experiments, different kinds of measuring devices, etc. In social sciences, this might come from multiple approaches to a single problem or statistical analysis (using correlation coefficients, T tables, etc.).

Its denial contradicts a rigorously corroborated fact (2): take, for example, the negation of the claim from above. Father Spitzer is not currently in his office (though multiple reliable witnesses can attest that he is in his office). Above, the affirmation of the statement confirms the evidence, whereas the denial of the proposition in the previous sentence contradicts the evidence. An example from science would be the denial that the earth rotates around the sun. Since it has been rigorously demonstrated that the earth does, in fact, rotate around the sun, the denial of this fact would contradict the evidence, thus rendering it unreasonable.

Intrinsic contradictions are impossible states of affairs (3): examples include square circles and finite infinities. Thus, a denial of a proposition that would lead to an intrinsic contradiction could not be true. Square circles of the same area in the same respect at the same place and time will not be able to exist in this universe or any other universe. Furthermore, they will not be able to exist in the future or the past any more than they can exist today.


J. G. Miller

Purposeful Universe Project Lead and Director, Media and Communications, The Magis Center