The Principle of Sufficient Reason (PSR) and the existence of God.

The principle of sufficient reason (PSR) tells us that everything has an explanation for why it exists. Even if we don’t know the specific cause, we still believe that there is a reason behind it. For example, when we see an avalanche, we might not know what caused it, but we don’t doubt that there is a reason for its occurrence.

Leibniz, a famous mathematician and philosopher, developed a cosmological argument for the existence of God using PSR. His argument can be applied to both an eternal universe or a created universe.

Leibniz asked if there is an explanation for the universe. This is sometimes put as, “Why is there something rather than nothing?” Dr. Edward Feser notes, and I think correctly, that the better question is, “Why are there any contingent things at all?” Things that are contingent don’t have to exist, but do because there was a cause for their existence. For example, you exist. But if your parents had not met you would not exist. The reason for your existence is your parents. Therefore, you are a contingent being. Things that exist which are not contingent are called necessary things. They exist without cause. Numbers are necessary. They exist out of necessity. Likewise, Leibniz reasoned, God is a necessary Being. He exists without cause. Thus, everything that exists either exists because they are contingent (they did not have to exist but do), or because they are necessary (they have to exist and cannot not exist.)

Philosopher Dr. Alexander Pruss has formed a basic Leibnizian argument. It goes like this:

P1 Every contingent fact has an explanation.
P2 There is a contingent fact that includes all other contingent facts.
P3 Therefore, there is an explanation for this fact.
P4 This explanation must involve a necessary being.
C1 This necessary being is God.

(The P stands for Premise. The C stands for Conclusion based on the premises.)

Dr. J.P. Moreland and Dr. William Lane Craig have a more modest version of PSR.

P1. Anything that exists has an explanation of its existence, either in the necessity of its nature or in an external cause.
P2. If the universe has an explanation of its existence, that explanation is God.
P3. The universe exists.
C1. Therefore, the universe has an explanation of its existence (from P1 and P3)
C2. Therefore, the explanation of the existence of the universe is God (from P2 and C1).

Craig asks and answers, “Is this a good argument?” He then notes that if the first three premises are more likely true than false, then the conclusion must follow. Leibniz developed an airtight argument for the existence of God using PSR.

Let’s assume we all agree on P3 – the universe exists.

P1 is a one-sentence explanation of PSR. Things that exist have an explanation of their existence. Most of those things are contingent (they did not have to exist but did or do exist). Necessary beings “exist of their own nature and so have no external cause of their existence” (Craig, Reasonable Faith, p. 107).

“All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together . . . We must assume behind this force the existence of a conscious and intelligent mind. This mind is the matrix of all matter.” 

– Max Planck

Some think of numbers, propositions, or sets as existing necessarily (that is, they would exist no matter what and could not have not existed). The only other candidate is what Dr. Max Planck, the “father of quantum physics,” called a “conscious and intelligent mind (German ‘geist’)” or spirit. It (this intelligent Spirit/Mind) would have to be non-physical since it is not contingent and would have existed before all things contingent and physical. It would have to be all-powerful to set contingency into motion. And, unlike contingent beings (here, I mean things that exist or have existed), they do not move from a potential thing to an actual thing but are non-potential and actual.

One could argue for an infinite regress – but that only moves the question “down the road.” And, according to the evidence we have at hand, the universe began to exist (I will discuss this in a later OP). Since nothing (not-any-thing) can cause nothing (not-any-thing), we have to have an initial first cause that exists necessarily. Or that the universe is a brute fact, but this seems counterintuitive and contrary to evidence, philosophy, and science. Regardless, this has been the standard atheistic position – that the universe exists without explaining its existence; it is simply inexplicable.

So what about P2? “If the universe has an explanation of its existence, that explanation is God.” Is this more plausibly true than false?

P2, Craig notes, is equivalent to saying, “If atheism is true, the universe has no explanation of its existence.” It exists without explanation – a brute fact and inexplicable. Therefore, the converse would be true, “If the universe has an explanation of its existence, then atheism is not true.” And if atheism is not true and is false, then God exists.

Since the universe exists of all space-time, matter, and energy – we know it to be contingent. If it is contingent, it has an explanation of its existence. And, if it has an explanation of its existence, then atheism is false, and theism is true. Additionally, a necessary being must be outside space-time, matter, and energy. It must be non-corporeal and non-contingent, powerful enough to create, extremely intelligent, and caring enough to create. This brings us back to Planck’s conscious and intelligent spirit/mind.

It seems to me that a proper response in an attempt to disprove PSR would be for the atheist to prove PSR is false or t show that P1 and P2 are more plausibly false than true. Otherwise, we are justified in accepting Leibniz’s PSR as a sound argument for the existence of God.

NOTE: Pruss has listed four possible difficulties with the Leibinzian Cosmological Argument and responds to them. You can find this in his chapter in The Blackwell Companion To Natural Theology (pp. 24-100), or read them online at: http://alexanderpruss.com/papers/LCA.html