The Leibnizian Cosmological Argument is one of my favourite arguments for God. The LCA can be summarised in this way:
- Every contingent fact has an explanation.
- There is a contingent fact that includes all other contingent facts.
- Therefore, there is an explanation of this fact.
- This explanation must involve a necessary object.
- This necessary object is God.
Today we are only going to discuss point 1. And this will probably not be our only discussion of this point, as there are many levels of counter arguments and responses to those that we will need to discuss at some point. This premise is called the Principle of Sufficient Reason.
A more general formulation (Taken from the SEP) is given as: For every fact F, there must be an explanation why F is the case. There are several good arguments for accepting the PSR, but so far there’s no proof of it.
First, if we do not accept the PSR, I would argue that we must accept some unfortunate consequences. I believe that I’m currently sitting in front of my laptop typing things into it. I believe this because I can see it. Because there are photons bouncing off my laptop (or emitted from the screen) and entering my eyes. But if the PSR is false, then there’s no reason to think that anything actually caused those photons to exist. Not just that I might be a brain in a vat being fed sensory information, or deceived by an evil demon like Descartes might suggest, but that there may be no explanation for the sensory information at all.
If we don’t take the PSR, then we can’t look at facts and try to work out the best explanation. Sherlock, for example, takes in a lot of details and provides usually a good explanation for why the facts are that way. But he never includes in his reasoning the option that there’s no explanation. Neither should we. We should look for explanations, and so we must always assume that there is one.
If the PSR is not true, why don’t we see lots of violations of it? If I saw a soccer ball materialize in front of me, I’d probably look for an explanation. But if the PSR weren’t true, there’d be no reason to look for an explanation. It could just be a brute fact that the soccer ball exists there. No explanation for why it is there.
Which brings me to the next argument: even if there’s not always an explanation, we ought to believe that there is one and look for it. Consider the example of the theory of evolution: what is the explanation for the variation of species? Normally, we’d say something like evolution via random mutation and natural selection. We’d justify that claim by pointing out the large number of observations that confirm it. But how do these observations confirm it? They confirm it via the PSR: we believe that evolution is true because it is the best explanation for our observations.
But how did we determine that there was an explanation here? The fact is that we didn’t, and we would have no way of doing so. We assumed there was, and we looked for it. But a Creationist who responds to the evidence for evolution with “Perhaps there’s no explanation” would be rightly ridiculed. We value explanations over no explanation, even if we can’t conclusively show that there is no explanation. We ought to believe there is one, even if there isn’t.
A more complex argument comes from Della Rocca. I link his paper below, and I will give a summary (and occasionally steal parts verbatim) of his argument here. First, he establishes that in every-day reasoning, we use something he calls “explicability arguments”. Something like this: no explanation for a state of affairs means that state of affairs cannot attain. Consider this: we have a scale with a weight on either side. If the weights are equal (and the scales are fair, and there are no outside influences), we know the scale will be balanced. How do we know this? Because there is no reason the scales would be unbalanced, there is no explanation as to how that would happen, so it cannot be the case. We reject the possibility of an unbalanced scale because it has no possible explanation. Or another example: suppose we have two substances. Suppose they are identical in every way, that they have the same chemical makeup, same structure, etc. One dissolves in water. We know that the other will dissolve in water too. Why? Because there is no reason why it would not, if one has the disposition to dissolve in water, how would the other fail to have this disposition? If they are identical, nothing could ground this difference, so we reject the possibility of them behaving differently.
In fact, it seems like avoiding inexplicability is a main motivator to naturalism or physicalism or materialism. We want to avoid believing in things that can’t be explained (such as the supernatural). The naturalist says that if it cannot be explained naturally, it does not exist. Again, they affirm the PSR in this context.
If we can use these arguments in general, then the PSR follows easily. Clearly we want to take a limited PSR in some local contexts. But can this kind of reasoning apply in general? Someone who denies the PSR might claim that it applies to some situations, but not others. But we claim that there is one example where we use inexplicability arguments where we can’t appeal to a local PSR without doing so arbitrarily and question-beggingly. And it is precisely the case in question in this argument.
What is it in virtue of which something exists? The existence of each thing that exists must be explicable. When we have causation, we ask why it is that this is a case of causation. So when we have something that exists, we ask why it is the case that this thing exists. The denier of the PSR attempts to draw a line somewhere, and explain why we can use a PSR in some contexts, but not in the existence context.
The denier of the PSR must draw this line in a principled, non-arbitrary way. This is because to draw the line in an unprincipled, arbitrary way is to say that there is no explanation or no reason why the law is drawn in this place. But to say that there is no explanation is to say that the PSR is false. And surely people cannot be allowed to assume the PSR is false when they are trying to argue against the PSR. That would be circular, I may as well assume God exists when trying to argue that God exists.
So of course, this line must be drawn in a principled, non-arbitrary way. And of course there is no such way. If you and I want to use the kind of explicability arguments above, then you and I need to come up with some reason why they work in some cases and not others. And unless we do come up with such a reason, we must accept the full PSR.