| The Leibnizian Cosmological Argument for God |
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- Everything that exists has an explanation of its existence, either in the necessity of its own nature or an external cause.
- The universe exists.
- If the universe does have an explanation for its existence, that explanation is God.
- Therefore, the universe has an explanation of its existence (from 1 and 2).
- Therefore, the explanation for the existence of the universe is God (from 3 and 4).
This brings us to the premise that’s the most controversial: premise 1. Why think that “Everything that exists has an explanation of its existence, either in the necessity of its own nature or an external cause”? Here I’ll borrow a bit from philosopher Richard Taylor’s illustration of finding a translucent ball in the woods. “How did it get there?” you ask. I reply, “There is no explanation for it being in the woods; the ball just exists inexplicably.” My response seems less plausible than the idea that there is some explanation for the ball’s existence. What if we enlarged the ball to the size of a car? Same problem: some explanation seems to be needed. How about a city? Same problem. A planet? Same problem. A galaxy? Same problem; increasing the size does nothing to remove the need for an explanation. How about if the ball were as big as the universe? Same problem. All things considered, it seems intuitively plausible that if a contingent thing exists, there is some reason why it exists, since it could have failed to exist.
One way a thing can have an explanation for its existence is to exist by the necessity of its own nature, but that isn’t an option for contingent things. The other way to explain why something exists is by reference to an external cause. But as far as the PSR is concerned, a thing that has an external cause as its explanation need not have begun to exist. For example, one idea is that the universe’s existence is being eternally sustained by God, similar to an eternal flutist eternally sustaining a note of music; God is the ground of all being and if God were to cease existing so would the universe. So the PSR does not require that contingent things begin to exist. That said, with the finite age of the known physical universe (among other considerations) it seems more likely to me that God created the universe as opposed to (merely) sustaining it in being.
Why do we need an external cause? Why not have an explanation from within, especially if the universe is infinitely old? While I think the universe is most likely of a finite age, not everybody agrees, especially atheists. With an infinitely old universe, we could conceive of each part of an infinitely long causal chain having an explanation for its existence, and one idea is that if we explain each individual element in the physical universe, then we explain the whole.
But this thinking commits the fallacy of composition, unjustifiably asserting something is true for the whole because it is true for the parts, e.g. because each part of an elephant is light in weight, therefore the whole elephant is light in weight. The fallacy in the case of explaining the universe reveals itself by considering the following scenario, borrowing largely from Leibniz’s illustration of copied geometry books. Suppose there have always been geometry books and that each geometry book has been copied from a previous book. So throughout the infinite past, there have been an infinite series of geometry books, each one copied from its predecessor. Although this is an explanation for each geometry book, it does not explain why we have an infinite series of geometry books rather than e.g. an infinite series of books on propositional logic, since that series of books could have been copied from eternity past as well, if geometry books could have. Nor does it explain why there is an infinite series of geometry books rather than no infinite series of books at all. Consequently, it does not explain the existence of the infinite series as a whole, even though it explains the existence of each individual book. That sort of thinking behind the infinite series of geometry books also applies to a physical universe with an infinitely long causal chain. Even though we have an explanation for each link in the chain, we can still ask why this infinite series exists rather than some other infinite series, and we can still ask why there exists an infinite series rather than no series at all. Explaining each part does not entail explaining the whole, and to think otherwise commits the fallacy of composition.
What about a causal-loop universe? One could argue that the universe has an internal cause of its existence in the sense of the universe causing itself, but that idea is metaphysically incoherent; for the universe to cause itself it would have to already exist. I know, time travel is a time-honored tradition of science fiction, but in the real world an agent going back in time to affect its own existence (say, a robot named Bob existing because it goes back in time to create itself) faces severe if not fatal problems (e.g. if such a thing were possible, it seems the aforementioned Bob the robot could also have gone back in time to destroy its younger self, thereby entailing that it doesn’t go back in time to destroy its younger self, thereby producing a self-contradictory state of affairs).
Still, suppose we believe that a causal-loop universe is metaphysically coherent. The causal-loop universe would itself be contingent and could have failed to exist, and the sort of problems affecting the infinitely causal chain afflict the causal-loop universe, in part because a causal-loop universe just is a specialized instance of an infinite past (albeit one that loops forever rather than a more linear infinite past). We can still ask why this particular circular causal chain exists rather than some other circular chain, and we can still ask why a circular causal chain exists rather than there being no such chain. Pointing to any component of the causal-loop universe (say, a time-travelling cause) won’t work to explain the universe’s existence because any such component is part of the very thing to be explained. It would be like trying to explain the existence of a circularly moving river (if such a thing were possible) by pointing to one half of the river in which water flows from that half to the other half of the river; this would do nothing to explain why the river as a whole exists rather than not (e.g. it wouldn’t explain why the river as a whole has water rather than there being no water to circulate). Similarly, pointing to any causal-flowing segment of a circularly-causal universe wouldn’t explain why the causal-loop universe as a whole exists rather than not.
Another way to look at premise 1 is that it’s the nature of rational inquiry to look for explanations for why things exist. We seek explanations for the existence of humans, of planets, of stars, and of galaxies. Avoiding all that and saying, “It all just exists inexplicably” would cripple science.
Challenging the PSR
Even if it is the nature of rational inquiry to look for explanations, a critic could say that this methodological aim to look for explanations doesn’t entail that explanations will always be found. A gold prospector might have the attitude of “Always look for gold” but that method doesn’t entail she will always find gold. So maybe not everything that exists has an explanation for its existence.
Maybe that’s true. In fact, maybe some things we think have explanations don’t have explanations at all. It’s logically possible (in the sense of not being self-contradictory) that the big bang theory is false and that the things that the big bang theory explains, like the cosmic microwave background radiation, simply exist with no explanation for their existence.
Still, that doesn’t seem to be the most rational way to go. The same holds true for a giant translucent ball (no matter how large it is). We should not exempt the universe from requiring an explanation if we have no good reason to do so, since it seems more rational to accept that there are explanations for the existence of things if we don’t have good reason to believe otherwise, especially if we have an explanation readily available and no evidence for the explanation being false. In regards to finding an explanation for the universe’s existence, if the only reason one rejects the proposed explanation in favor of “there is no explanation” is that one just doesn’t like the proposed explanation very much, it doesn’t seem like such a person has a good enough reason (imagine if someone rejected the big bang theory for that reason!). One could argue that, all things considered (the nature of rational inquiry etc.) we should accept PSR unless we have good reason to believe that it is false, including when it comes to the existence of the physical universe.
Another consideration is to imagine the shoe being on the other foot; if the best known explanation for the existence of the physical universe were devastating to theism instead of devastating to atheism, I suspect atheists would criticize a theist’s “the universe has no explanation” response, and they would be right to do so. The rational thing to do is to accept that there is an explanation for the existence of the universe if we don’t have good reason to think otherwise.
Do we have such a reason? Here’s the best atheist position I can think of. While contingent things that begin to exist require an explanation of their existence via an external cause, contingent things that exist eternally don’t necessarily have external causes and thus don’t necessarily require an explanation of their existence. Such contingent things exist eternally and inexplicably. The atheist can argue that the physical universe fits this category: it is contingent but eternal and doesn’t have an explanation of its existence.
The first thing to say is that it isn’t necessarily the case that if a contingent thing exists eternally that no explanation for its existence is needed. For example, suppose we humans learned of an eternally existing monument at the center of the universe that says, “I, the Lord thy God, am the sustainer of the universe and have sustained it throughout all eternity” (if questions of different languages bother you, imagine further that it displays this message through a kind of mechanical telepathy such that anybody who looks at the monument sees the message in her own language). A response like, “Well, the monument existed eternally, so no explanation is needed for why this monument exists” doesn’t seem convincing. Or to use a more decidedly nontheistic example, imagine a three-dimensional hologram projection that exists eternally and is also eternally sustained by a hologram projector. Even though the hologram exists eternally, we have an explanation for the hologram’s eternal existence. The hologram is contingent and it could have failed to exist, and there is an explanation readily available for why it exists rather than it not existing. With that in mind, suppose some contingent thing X meets the following conditions:
- X is eternal but contingent (it could have failed to exist).
- There is an explanation for why X exists .
- It is the only explanation of X’s existence that is a live option.
- There is no reason to believe that this explanation for X’s existence is false.
It’s possible that the atheist thinks there is a good reason to believe the transcendent personal cause explanation is false and thus that condition 4 is not met, though I have yet to see such a reason. In any case, it seems clear that for the atheist to rationally reject the explanation, some good reason will need to be given, i.e. the ball is in the atheist’s court. Such atheists don’t have to swing at the ball, but if they don’t, they’ll lose the game.
At the end of the day, the theist can grant for sake of argument that maybe some eternal contingent things don’t require explanations for their existence and still argue that all things considered (e.g. the four conditions mentioned earlier regarding eternal contingent things, and what would be rational to do if the shoe were on the other foot) we are rational to accept that the universe has an explanation of its existence, giving us this version of the LCA (call it LCA 1C):
- If the universe exists it has an explanation of its existence, either in the necessity of its own nature or an external cause.
- The universe exists.
- If the universe does have an explanation for its existence, that explanation is a transcendent personal cause.
- Therefore, the universe has an explanation of its existence (from 1 and 2).
- Therefore, the explanation for the existence of the universe is a transcendent personal cause (from 3 and 4).
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