Gottfried von Leibniz, German philosopher and mathematician, saw that the question of questions, the most fundamental, most important, most life-changing question was, "why is there something rather than nothing?"1 From this simple question, Leibniz was able to demonstrate the existence of God. As his argument might not be as familiar as some others, I thought I might quickly review it here.
A short summary of this argument, as provided by William Lane Craig, runs thus,
1. Everything 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. The universe has an explanation of its existence
5. Therefore, the explanation of the universe's existence is God2
We Hold These Truths to be Self-Evident...
Premises one and three are self-evidently true. Science is precisely man's attempt to understand the causal relationships within the physical, material universe. If things can exist for no reason, with no explanation, then science is impotent and meaningless, for it can do no more than look at something, anything, and say "maybe it just, for no reason, is." That would apply, not just to the universe, but to a 500 pound purple gorilla with yellow spots sleeping in my bed when I go home tonight. Just as any reasonable person wouldn't accept “its just in your bed" as an explanation for the gorilla, so too any reasonable person wouldn't accept "it just is" for an explanation for anything else.3 Note, our first premise doesn’t force us to posit something beginning to exist for it to require an explanation for its existence (unlike in the kalam cosmological argument). Premise one simply states that everything that exists (even if it has always existed) must necessarily have an explanation for its existence. Nothing simply is for no reason whatsoever. Premise three, "the universe exists," is even more undeniable, for if the universe doesn't exist, then neither does anyone exist to deny our argument (or to make it). No one, except madmen or atheist philosophers desperately trying to avoid the conclusion of this argument, would deny either premise one or premise three.
Premise four logically follows from premises one and three. Premise four cannot be false if premises one and three are both true (as we will see below). Therefore most attempts to defeat this argument center on premise two. Let's take a closer look at this contested premise.
"If the universe has an explanation of its existence, that explanation is God."
While premise two might seem bold at first glance, it really is just as inescapable as the other statements in our argument. We know, from premise one, that everything must have an explanation for its existence, this clearly includes the universe (to exempt the universe would be a gross use of the fallacy of begging the question). This explanation can either be intrinsic to the universe, a feature ofthe universe that makes it have to exist or it could be something extrinsic to the universe. If we say the explanation for the universe is intrinsic, that is if we attempt to create a pseudo-god from the universe, we run into immediate and irreconcilable problems. Modern Big Bang Cosmology has shown us that the universe itself,
- began to exist approximately 13.8 billion years ago (and thus isn’t eternal)
- the universe, including its fundamental laws and particles, could have been different than they are. That is, the universe we have isn’t the only possible universe that could have existed.
But both of these scientific facts show us that the universe we inhabit does not exist necessarily. The universe didn’t exist 13.9 billion years ago and could have never existed at all (or another universe with different properties could have existed instead of this one). Therefore the universe doesn’t explain itself (i.e. it doesn’t exist necessarily) and must, therefore,have an explanation outside of itself.
What must this extrinsic explanation be? Could it be something other than God or is our second premise justified? We can know a few things about this “explanation” simply by reflecting on what it must mean to be the “explanation” of the universe. For example:
- as the universe includes all of space, an extrinsic explanation must be unrestricted by space, and thus present everywhere (omnipresent).
- as the universe includes all of time, an extrinsic explanation must be unrestricted by time, and thus present always (eternal).
- as the universe includes all matter, the extrinsic explanation must be immaterial.
- as the extrinsic explanation of all space, time, and matter, the explanation must be incredibly, indeed all, powerful (omnipotent).
This omnipresent, eternal, immaterial, omnipotent explanation for the existence of the universe is clearly what men mean when they speak of “God.” Premise two, then, also holds.
If all our premises are true, the conclusion, "the explanation of the universe's existence is God" must necessarily follow, as long as the logic undergirding Leibniz's argument is sound. Let's examine this logic more closely.
Our argument consists of two syllogisms, sharing statement four above (as a conclusion in the first syllogism and a premise in the second). The first syllogism runs:
All things that exist have an explanation for their existence.
The universe is a thing that exists.
Therefore, the universe has an explanation for its existence.
This is a simple and clearly valid syllogism in the same form as the common logic 101 example:
All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.
Our second syllogism is a little more complex being:
If the universe has an explanation for its existence, that explanation is God.
The universe has an explanation for its existence.
Therefore, the explanation of the universe is God.
This is a particular kind of syllogism, a hypothetical syllogism. To see if it works we'll use a little "symbolic logic" which is very easy, if a bit unfamiliar. In testing a hypothetical syllogism we use the letter "p" for our antecedent (the "if" part of our "if...then" proposition) and "q" for our consequent (the "then" part of our "if... then" proposition). So our argument is:
p ⊃ q
antecedent - the universe has an explanation (let this be "p")
consequent - that explanation is God (let this be "q")
⊃ - means this is a hypothetical syllogism (a "if... then" argument)
∴ - means "therefore" (signals our conclusion)
For this type of argument to succeed in proving its conclusion, the syllogism must either affirm the antecedent (the second line is "p") or deny the consequent (the second line is “not q”), if it denies the antecedent (the second line is "not p") or affirms the consequent (the second line is "q") the argument fails to conclusively prove anything (except for the poor logic of the arguer). Thus, all we have to do, once we put the argument into its symbolic form, is see if the second term is “p” or “not q” (which means its valid) or if it is “not p” or “q” (which means our argument has failed). As can clearly be seen above, our second line is "p" meaning this second syllogism is also valid.4
Thus, our premises, for both syllogisms, are true, our logic, for both syllogisms, is valid and none of our terms, in either syllogism, are ambiguous (i.e. they maintain the same meaning throughout the argument). Having met those three tests we know, for certain, that our conclusion must be true. Atheism5 is refuted and we see, with the help of Leibniz, that God must exist.
1. G.W.F. von Leibniz, "The Principals of Nature and Grace, Based on Reason," in Leibniz Selections, p 527
2. Craig, William Lane, On Guard: Defending Your Faith with Reason and Precision, chapter 3
3. This would, of course, include God, as Leibniz himself would be the first to recognize. If everything that exists has an explanation of its existence and God exists, God too must have an explanation for His existence (otherwise theists would be guilty of "special pleading" in trying to exempt God from the universal application of premise one. God's explanation for existence is found within His nature. He is existence (ipsum esse subsistens) and thus cannot fail to exist. God's reason for existence is intrinsic, but He nonetheless has an explanation of His existence. God, then, is not an exception to premise one, as indeed nothing can be.
4. Those interested in more in depth discussion of the rules of logic are advised to turn to Kreeft, Peter, Socratic Logic.
5. Atheism here refers not to “lack of belief” but to the metaphysical position that God does not exist. More HERE for a defense of this use of “atheism.”