Teachings of the Catholic Church

* Naturalism:  The contention that everything in the universe can be fully explained by the laws of nature because, in fact, there is absolutely nothing else in the universe beyond the laws of nature.

Why Naturalism Is Self-Defeating:

1. If Naturalism is true, then every finite thing or event must be (in principle) explicable in terms of the laws of nature.  (We add the caveat in principle because we are not going to demand that naturalists, at any given moment, should have found the detailed explanation of every phenomenon.  We will allow that many things will only be explained when the sciences have made further progress.)

In other words, nothing can escape the causal nexus of Naturalism:  every thing and every event must be the result of the non-rational, ineluctable forces of nature.

2. If this is true, then the mind (along with its thoughts and conclusions) must be, like every other thing or event, simply the result of the non-rational, ineluctable forces of nature.

3. If this is true, then there would be no way of distinguishing between "true" thoughts or conclusions and "false" thoughts or conclusions.  All thoughts and conclusions whatsoever would merely be the result of the non-rational, ineluctable forces of nature.  Thoughts would be no more "true" or "false" than any other result of a natural process.  A car rusting is no more "true" or "false" than a rock falling or a comet orbitting:  all are simply the results of certain, prior causes.

4. But if we suppose #3, then we have no way of concluding that Naturalism is true, because the conclusion we must draw from Naturalism, is that there are no such things as "true" arguments or "false" arguments, "true" conclusions or "false" conclusions, "true" thoughts or "false" thoughts.  To accept Naturalism as true, it must be possible to have a "true" conclusion.  But this is precisely what Naturalism denies!

5. Thus, since Naturalism makes it impossible to accept anything as "true" or "false," it makes it impossible for us to accept Naturalism as "true" or "false."  The attempt to convince us that Naturalism is true presupposes an ability that Naturalism denies we have.

As C.S. Lewis has said:

"It follows that no account of the universe can be true unless that account leaves it possible for our thinking to be a real insight.  A theory which explained everything else in the whole universe, but which made it impossible to belive that our thinking was valid, would be utterly out of court.  For that theory would itself have been reached by thinking, and if thinking is not valid, that theory would, of course, be itself demolished.  It would have destroyed its own credentials.  It would be an argument which proved that no argument was sound -- a proof that there are no such things as proofs -- which is nonsense."
 

Or again, as the scientist J.B.S. Haldane has said:  "If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true ... and hence I have no reason for supposing my brain to be composed of atoms" [or to believe that my mental processes are determined wholly by the motions of atoms.]

6. Since the arguments of the Naturalists are contradictory -- they presuppose what they deny -- they are fundamentally irrational and thus have no claim on our assent (because, in fact, they claim that our assent is impossible).