Christian Apologetics - Philosophical Arguments

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In this brief article I present five philosophical arguments for the existence of God. I need to warn you, however, that they are quite intellectual and … well … philosophical! If you have had training or previous experience in philosophy and logical reasoning these arguments are convincing, but for the average person the arguments may seem somewhat esoteric.

Philosophical Argument 1: The Ontological Argument

Ontology is the philosophical study of the nature of being: the nature of existence itself. This is an argument from pure logic alone and, in my opinion, it is worthy of consideration. The ontological argument was first proposed by Archbishop Anselm of Canterbury in the 11^th century but the original wording is somewhat cumbersome:

“Even a fool, when he hears of a being than which nothing greater can be conceived understands that, than which nothing greater can be conceived, cannot exist in the understanding alone. For suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater. Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality.”

Confused? I don’t blame you! Let me translate the argument into contemporary language and break it down into its individual logical components:

1. It is a conceptual truth that God, by definition, is the greatest possible being that can be imagined.

Most atheists would agree with this opening proposition. If God does exist, he is the greatest possible being that can be imagined. If you can imagine something greater than God, then the new thing that you are now imagining is God and the first thing you were imagining wasn’t God. This hinges on the foundational definition of God: that God is the greatest being that can be imagined.

2. God exists as an idea in the mind.

Atheists agree with this too. In fact, they would say that this is the ONLY place where God exists – purely as an idea in people’s minds.

3. A being that exists as a reality as well as an idea in the mind is greater than a being that exists only as an idea in the mind.

This is simple logic. An imaginary friend can’t give you a hug, or help you build a carport or kick a soccer ball with you, whereas a real friend can do those things. Thus, a real being is greater than an imaginary being.

4. Thus, if God exists only as an idea in the mind, then it is possible to imagine something that is greater than God (that is, a being who exists as BOTH an idea in the mind AND a reality).

However, we’ve already defined God as the greatest possible being that can be imagined. And you can’t imagine a greater being than God. Thus:

5. But we cannot imagine something that is greater than God (for it is a contradiction to suppose that we can imagine a being greater than the greatest possible being that can be imagined.)

6. Therefore, God exists.

This is a rare instance in philosophy where an existential claim can be proved from a conceptual claim. In this case the deduction of God’s existence arises directly from the conceptual definition of God. This argument is founded entirely upon the opening premise. Provided you agree with opening definition of God, the argument is completely watertight. It is flawless logic.

Some sceptics argue that the same kind of argument could be made to prove the existence of unicorns, in the sense that a unicorn that exists as a reality as well as a mere idea is greater than a unicorn that exists as a mere idea only, and therefore, unicorns must exist. But this does not follow, because the necessity of being the greatest possible entity that one can imagine is not intrinsic to the fundamental definition of a unicorn. The concept of the greatest possible being that can be imagined only applies to God and is intrinsic and essential to a meaningful definition of God.

Philosophical Argument 2: Leibniz’ Contingency Argument

Gottfried Leibniz was a 17th Century German Philosopher, who posed a simple yet profound question; “Why is there something rather than nothing?” He then proposed a logical series of propositions that lead to the conclusion that God is the only reasonable explanation for the existence of the universe and that God must, therefore, exist.

I. Anything that exists has an explanation of its existence.

2. If the universe has an explanation of its existence, that explanation is God.

3. The universe exists.

4. Therefore, the explanation of the universe’s existence is God.

This is considered by many to be a logically airtight argument. If the first three premises are true, then the conclusion is unavoidable. So, the only way to reject the conclusion is to disprove one of the first three premises.

The third premise, that the universe exists, is undeniable (although extremists might try to argue that the universe we perceive might only be an illusory construct into which we are all plugged – like the Matrix in the film of that name). With the exception of that rather ridiculous proposition, if an atheist is going to defeat this argument, they must disprove either Premise One or Two

Premise one, the proposition that anything that exists has an explanation of its existence, is sometimes argued against by those who claim that the universe has always existed and doesn’t need an explanation. In other words, they claim that the universe is uncaused.

But this is strongly refuted by the findings of modern cosmology which point conclusively to the universe having a finite beginning at some point in the distant past. Several findings point to this conclusion: Einstein’s theories of General and Special Relativity, the doppler red shift of expanding and receding galaxies in our expanding universe, the discovery of Cosmic Microwave Background Radiation (CMBR) left over from a possible ‘big bang’ at the beginning of space-time, and extrapolations from the Second Law of Thermodynamics which point out the impossibility of eternally existing universe that has not yet reached thermal equilibrium. I have explained all of these in great detail in my book, 7 Reasons To Believe, and I have a page on this website dedicated to explaining this evidence HERE.

The upshot of this evidence is that modern cosmologists are now having to contend with the fact that the universe had a finite beginning. And if that is the case, such a beginning demands an explanation.

A second objection to this first premise is the counter-argument that if the universe requires an explanation, then so must God (if he exists). In other words, we can’t propose God as an explanation for the universe’s existence, because we must then explain how God came to exist.

In answer to this counter-argument, Leibniz differentiated between things that exist contingently and things that exist necessarily. Almost everything exists contingently; they have a cause. But some things exist by the necessity of their own nature; it is impossible for them not to exist. The only two things that fall into this second category are abstract numbers and God. In the latter case, God, by definition, cannot exist contingently, otherwise he is not God. In other words, as soon as you start claiming that someone or something else must have made God, then what you have just referred to as God is clearly NOT GOD; he is just another created being. And then you are left with an infinite string of causality – who made the being who made God? And who made the being who made the being who made God? And so on.

The only logical definition of God is that he exists APART from temporal causality. This makes perfect sense, because only a being who exists apart from temporal causality could have created a temporally contingent universe. Thus, God exists necessarily not contingently.

A third possible objection to Leibniz’s second premise is the argument that the universe is the one exception to the rule of causality. In other words, everything else in the universe must have an explanation for its existence, but the universe itself doesn’t need an explanation; it just came into existence from nothing, randomly, without any cause. But this argument defies all laws of common sense, logic and science. It is an argument arising from sheer desperation in order to avoid facing the possibility of a transcendent cause.

Premise one, therefore, is philosophically unassailable: Anything that exists has an explanation of its existence. We can now add another detail to this by stating, Anything that exists has an explanation of its existence either in the necessity of its nature or in an external cause. Arguments that attempt to refute this premise fail.

This brings us to Premise 2: If the universe has an explanation of its existence, that explanation is God. On the surface, this may seem to involve a massive jump in logic, so let me explain the underlying logical flow of this premise:

> The universe consists of all of space-time, energy and matter

> If the universe has a cause, that cause cannot be part of the universe.

> The cause must be immaterial, uncaused and non-temporal – beyond space and time.

> The only things that fit that description are abstract concepts like numbers, and a God.

> Since abstract concepts and numbers can’t create matter, the only possible cause is God.

I regard this as an airtight logical argument, but it is not without its detractors. Ardent atheists will argue that there must be a logical, natural explanation for the universe that doesn’t involve a supernatural cause – we just haven’t discovered it yet! I have written and spoken extensively elsewhere in response to this claim, but for our purposes here, I make the following brief points:

I. This counter-argument effectively turns future science into a ‘God of the gaps’ by proposing that “we don’t know how the universe could have created itself, but future science will one day tell us.” This is a statement of great faith, particularly when one considers the points that follow here.

2. All the current theories that are currently proposed regarding how the universe could have created itself are not scientific theories but exercises in imaginative fantasy because they are not based on observable, repeatable, measurable evidence. (I deal with these theories in some of my books and videos).

3. These theories ALL rely on pre-existing forces or causes which, themselves, must also be contingent and, therefore, require an ultimate cause. They merely push the question of ultimate cause further back without proposing an ultimate answer to the question of causation. These supposed pre-existing forces or causes that underpin all current speculative ‘theories’ of the origin of the universe are, themselves, part of the physical universe or its underlying subspace or quantum structures. The question then needs to be asked, “Where did THEY come from?” (For a more detailed evaluation of current speculative theories of the universe’s beginning, watch out for Episode 2 of the video and podcast series, Evidence for Belief).

4. Ultimately, all imaginative speculations regarding how the universe could have created itself fail because they ignore a simple principle of logic and common sense: the physical universe had to have been created by something or someone beyond the physical universe. Nature can’t be created by nature; it had to be created by something beyond nature; something supernatural (which is what the term supernatural means).

Leibniz’s Contingency Argument is a powerful philosophical argument that confronts us with the need to explain the existence of the universe and, in so doing, points very convincingly to the existence of metaphysical cause. From a purely logical perspective, whatever caused our universe must be extremely powerful, uncaused, necessarily existing, non-contingent, immaterial and non-temporal. Anything or anyone less than this could not have created a material, temporal, contingent universe.

We have a name for such an uncaused, immaterial, non-temporal, non-contingent, all-powerful being. We call such a being God.

Here is a link to a helpful video on Leibniz’s Contingency Argument.

Philosophical Argument 3: The Cosmological Argument for God’s Existence

Philosopher and apologist, William Lane Craig, has modified Leibniz’s Contingency Argument and formulated his own take on the Kalam Cosmological argument. It goes as follows:

I. Whatever begins to exist has a cause.

2. The universe began to exist.

3. Therefore, the universe has a cause.

4. That cause must be spaceless, timeless, uncaused, immaterial and powerful.

5. The best explanation is God.

This is an even clearer argument than Leibniz’s because it deals not merely with things passively existing, but with them beginning to exist. This places more emphasis on the logical necessity of a cause and points out the absurdity of a temporally past-infinite universe. Much of the same reasoning that underpins Leibniz’s Contingency Argument also underpins this argument.

Here is a link to an excellent video from William Lane Craig’s organisation, Reasonable Faith, which explains the Kalam Cosmological Argument in detail, including additional scientific evidence for the universe having a finite beginning.

Philosophical Argument 4: The Impossibility of an Infinite Regression of Events

This argument was proposed by the 13th century Catholic philosopher and theologian, Thomas Aquinas. It supports Leibniz’s Contingency Argument and is a helpful corollary to it. Aquinas taught that it is not possible to regress to infinity in efficient causes. In simpler terms, this means that there cannot be an infinite regression of causes for an event, with each cause being caused by a prior cause; there must eventually be a first cause.

Thus an infinite regression of causes cannot exist in the real, material world. While the concept of infinity is valid conceptually in mathematics, infinity only exists as an abstract concept and not as an actual number in the material universe. This argument is used to prove that the universe cannot have existed eternally but must have had a finite beginning.

Aquinas’s argument is built upon an earlier argument posed by the Persian philosopher, Al-Ghazali, in the Middle Ages. He stated:

“If there were an infinite number of events in the past, we would never have arrived at the present.”^[i]

This simple, yet profound philosophical argument cannot be refuted without dismissing the laws of logic. Think about it. If time is a corridor and you started in the present and went back in time towards infinity past, you would never reach infinity past. You can’t reach infinity past from the present: you will never get there! In the same way, you can’t reach the present from infinity past. It is impossible. Al-Ghazali’s theorem proves that the universe cannot have existed forever. Thus, Al-Ghazali concluded;

“An infinite number of things cannot exist.”^[ii]

I would amend this to state that “an infinite number of things cannot exist in a temporal universe” (one which is constrained within space and time). This applies to increments of time (seconds) as well as physical matter.

The German mathematician, David Hilbert, supported this axiom in his thought experiment known as ‘Hilbert’s Hotel’ where he demonstrated the impossibility of an infinite set of events existing in the real world. This applies to an infinite set of anything, but in this case, we are specifically talking about an infinite number of seconds.

While this argument, the impossibility of an infinite regression of events (and thus of time), does not prove God’s existence ‘per se’, it does prove that the universe must have had a beginning. This, in turn, necessitates an explanation of its cause – which we have already seen must lie outside the realm of our contingent space-time continuum.

Philosophical Argument 5: The Moral Argument for God’s Existence

This is perhaps the most persuasive philosophical argument for God’s existence. Space does not permit a full discussion of this argument here, so I have dedicated a separate page of this website to this argument. It can be found here: The Moral Argument For God’s Existence

FREE RESOURCES:

Slide Presentations:

AP1A Apologetics Introduction (.ppx)

This slide presentation introduces the topic of Apologetics generally and also points to the turning tide in the ongoing debate between theism and atheism.

AP1B Philosophical Arguments (.ppx)

This slide presentation outlines some of the main philosophical arguments that point to a theistic first cause for the universe. Some people may find these arguments very abstract and difficult to comprehend. If so, don’t worry! Just move on to some of the less abstract topics offered on SmartFaith.net.

Instructions For Downloading PowerPoint Presentations: Click the PowerPoint link, then click the “Open” drop down box at the top right of the screen and select “Open in PowerPoint Online” or “Open In PowerPoint”. When the presentation is opened, click the “Notes” tab at the bottom right of screen. This will open the Presenter Notes, which provide a detailed explanation of each slide. Some slides also have embedded video content, which can be viewed via the standard “play” button or by clicking the image.

Essential reading for anyone who is serious about defending their faith!