Thursday, July 7, 2011

Question about PSR

Tonight we consider a question that came in to me:

I wonder if you could help me understand something about both the Leibnizian CA and the Kalam CA. Is there a difference between the PSR in the LCA and the 2nd premise in the KCA? They sound the same to me. I do have a problem with the PSR though, namely that if we reduced everything to explanations, e.g. "Why did the bottle fall? Because the law of Gravity caused it to." We would be led to a point where an explanation seems to be unnecessary. In the example above, it would be something like "Why is the law of Gravity like this and not like anything else?". Now if we say that the natural laws are necessary therefore do not need an explanation, then the argument for God fails because a completely naturalistic account of how this all came to being is more plausible. But if we say that there is no explanation as to why the laws behave in the way they do, then this seems to violate the 2nd premise of the KCA, in which it is possible to say that the universe just happened. I'm especially curious with how the PSR would work with the laws of logic, and God's relation to logic. What if logic were just a human construct based of science? If that were true, then Christianity is in trouble!

The PSR (Principle of Sufficient Reason: It states everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause) is very different than the second premise, for two reasons. (1) The PSR as presented in the modern LCA or the argument from contingency is compatible with a necessary natural being, person, thing, or state of affairs that did not begin to exist, while the second premise affirms that the universe began to exist (to be clear: the PSR is compatible with both necessary and contingent things that exist or did not begin to exist). As such, the PSR could apply even if (2) is false or true, meaning they are not identical. (2) The content of the premise "the universe began to exist" cannot entail explanations of everything else that exists without begging the question against theism.

Now you seem to be on that track by asking "what if someone postulated the physical laws are necessary?" But that's a huge assertion that requires at least some evidence. It won't do to say that the laws are all we know, again for two reasons: 1. That's an appeal to ignorance, and 2. To say something is necessary in the absence of any evidence in a positive category is to say that its negation violates some known necessary truth or entails a contradiction. The bottom line is, they won't be able to give you any logical contradiction without begging the question.

Now if we say there is no explanation for the laws of nature, I do not think this violates the second premise of the kalam. Why not? Well, consider we have a postulated God who, without the world, decides to create the universe. He wants there to be humans, but doesn't want to force the constants and laws. So he creates the idea of quarks, say. Then, he consults a randomizer that only takes into account universe-like domains that are built upon quarks, this God being content to accept whatever the randomizer throws out. Now, as it turns out, the randomizer spits out this universe, with these physical laws. I think we can see the universe still could have plausibly began to exist with the constants having no causal explanation. Now of course, you may reply, what kind of ridiculous experiment was that?! The odds are so unlikely that it would never happen in one shot! And thus, what we see is that if the physical laws have no explanation, then really it contradicts the second premise of WLC's argument from design.

In any case, you're forgetting that third alternative: the laws of nature act the way they do because God constructed them that way. That no atheist will accept this premise does nothing to undercut its force, nor does it avoid the problematic alternatives if they choose to reject it. But in any case, in order to avoid the highly intuitive PSR, they'll need to come up with a counterexample, and the universe just ain't it.

As to the laws of logic, these cannot be denied without their usage. See my article, "A New Defense of the Law of Noncontradiction" here on this site.


  1. Another point is that the KCA is not at all the PSR. The Principle of Sufficient Reason is the idea that everything which exists must have a sufficient reason. This is greatly different from saying "Everything that began to exist has a cause."

    With the PSR, we're discussing sufficeint reasons, not causes. For example, God did not begin, so the KCA would not apply to God. But the PSR does, and the sufficient reason is God's necessary existence.

    Check out Alexander Pruss's book on the PSR, it's a great read.

  2. Thanks JW! I've been meaning to read it. So far, I have only read his chapter on it in Blackwell's Companion to Natural Theology. And of course, I follow his blog.

    Interestingly, the questioner contacted me and explained he in fact meant the first (causal) premise, and my response was very very similar to yours!


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