The Leibnizian Contingency Argument
In 1697, the German polymath Gottfried Wilhelm Leibniz posed what has been called the deepest question in philosophy: why is there something rather than nothing? His answer - the argument from contingency - does not depend on the universe having a beginning. Even an eternal universe would still demand an explanation for why it exists at all.
The Deepest Question
Look at anything around you - a tree, a mountain, the planet itself. None of it had to exist. Each thing depends on something else for its existence: the tree on a seed, the mountain on plate tectonics, the planet on a collapsing cloud of stellar dust. Philosophers call such things contingent - they exist, but they could have failed to exist.
Leibniz noticed that this raises a question that never goes away, no matter how far back you push the chain of explanations: why is there anything at all? Even a complete physical account of how each thing came from prior things would not answer it - because the question applies to the whole collection. Why is there a universe of contingent things rather than simply nothing?
Note carefully how this differs from the Kalam argument of the previous lesson. The Kalam argues from the universe's beginning; the contingency argument argues from the universe's dependence. If a skeptic insists on some past-eternal cosmology, the Kalam is contested - but Leibniz's question still stands untouched. An eternal universe would still be a contingent universe, and its eternal existence would still cry out for an explanation.
The Formal Argument
William Lane Craig formulates Leibniz's argument in three premises:
- P1Everything that exists has an explanation of its existence - either in the necessity of its own nature, or in an external cause.
- P2If the universe has an explanation of its existence, that explanation is God.
- P3The universe exists.
- β΄From P1 and P3, the universe has an explanation of its existence - and from P2, that explanation is God.
The logic is airtight; everything turns on the two substantive premises. Premise 1 is a version of the Principle of Sufficient Reason (PSR), which philosopher Alexander Pruss - whose strengthened formulation you met in the Kalam lesson - has defended at book length: contingent facts do not simply hang in the void unexplained. Premise 2 sounds bold, but notice: it is exactly what the atheist typically affirms. To say "if God does not exist, the universe has no explanation - it is just a brute fact" is logically equivalent to saying "if the universe has an explanation, that explanation is God."
Why the Explanation Must Be a Necessary Being
Premise 1 allows only two kinds of explanation: a thing exists by the necessity of its own nature, or through an external cause. Which is the universe?
Not the first. Nothing about the universe suggests it exists necessarily. Its fundamental particles could have been different or absent; its constants (as the next lesson on fine-tuning shows) could have taken other values; physicists routinely model universes with different laws, or none at all. A necessarily existing thing could not have been otherwise - and everything we know about the universe says it could have been otherwise.
So the universe requires an external cause. But since the universe includes all of space, time, matter, and energy, its cause must be outside all of these - non-physical, non-spatial, non-temporal, and itself necessary (otherwise it would just push the question back another step). Only two candidates for necessary, immaterial existence have ever been seriously proposed: abstract objects (like numbers) and an unembodied mind. But abstract objects, by definition, stand in no causal relations - the number 7 has never caused anything. That leaves a necessarily existing, transcendent mind. As with the Kalam, the argument lands on what theists have always meant by God - but by an entirely independent route.
This five-minute animation from Reasonable Faith - the same series as the Kalam and fine-tuning videos in this track - presents Craig's formulation of the contingency argument. Watch for its central illustration: hiking in the woods, you find a translucent ball lying on the forest floor, and you naturally wonder how it got there. Enlarging the ball - to the size of a car, a house, a planet, the entire universe - does nothing to remove the need for an explanation. Size and age are irrelevant; contingency is the issue.
Leibniz' Contingency Argument · Reasonable Faith (drcraigvideos) · Watch on YouTube · reasonablefaith.org
Common Objections
"The universe is just there. It's a brute fact - it doesn't need an explanation."
This was Bertrand Russell's reply: "The universe is just there, and that's all." But notice what it costs. The entire scientific enterprise runs on the conviction that things have explanations - abandon that conviction at exactly one convenient point, and you commit Schopenhauer's taxicab fallacy: riding the principle of explanation as far as you like, then dismissing it when it arrives somewhere unwelcome. If "it's just there" is an acceptable answer for the universe, why was it never acceptable for lightning, disease, or planetary motion?
"If everything needs an explanation, what explains God?"
Premise 1 already answers this - and it is not special pleading. It allows two kinds of explanation: external cause, or the necessity of a thing's own nature. God, as classically conceived, exists by the necessity of His own nature; His explanation is internal, like the explanation mathematicians give for why 2 + 2 = 4. The universe manifestly does not exist this way - which is the whole argument.
"Why can't the universe itself be the necessary being?"
Because nothing in the universe - and no configuration of it - shows any mark of necessity. A necessary being could not have been otherwise in any respect; yet the universe's particles, constants, laws, and initial conditions all appear thoroughly arbitrary, and physicists treat alternative values as genuinely possible (this is what makes the fine-tuning discussion of the next lesson meaningful at all). Matter and energy are precisely the kinds of things that could have been different or absent.
- The contingency argument works even if the universe is past-eternal. Why does that make it a valuable companion to the Kalam rather than a duplicate of it?
- Is the Principle of Sufficient Reason something we know, something we assume, or something science presupposes? What happens to inquiry if we abandon it?
- Is "the universe is just a brute fact" an explanation, or a refusal to explain? Is there a principled difference?
- Why can't abstract objects like numbers serve as the necessary foundation of contingent reality?
How does the contingency argument differ from the Kalam Cosmological Argument?
Leibniz's contingency argument shows that a universe of contingent things requires an explanation grounded in a necessarily existing, transcendent, personal being - and unlike the Kalam, it does not depend on the universe having a beginning. Together with the Kalam, it forms a two-pronged cosmological case: whether the universe began or is eternal, its existence points beyond itself. This argument traces from Aquinas's Third Way through Leibniz to contemporary defenders like Alexander Pruss and William Lane Craig.
Related lessons in this track: The Kalam Cosmological Argument · Something From Nothing? The Quantum Vacuum Fallacy