Thoughts on the Argument from Reason

Victor Reppert popularized one of my favorite arguments for some sort of dualism. The argument first appeared in the 3rd chapter in C.S. Lewis' book Miracles called 'The Cardinal Difficulty in Naturalism'. I can't reproduce it here perfectly from memory, but I'll write what I remember.

According to Naturalism, we are purely material objects. There is no part of us that is not made of matter. But then a question arises: how is it that we come to call our own thought rational? For, presumably, if something is purely material, all of its parts are non-rational. If we have 10 grains of sand or a billion grains of sand, we still have a bunch of sand.

Now, the scientists tell us that matter is completely governed by the law of cause and effect. This law governs certain bahavior of matter called events. Thus, if our minds are nothing but matter, then our minds are nothing but various events governed by the law of cause and effect. By definition, if X is wholly material, and therefore nothing but events, and therefore governed by the law of cause and effect, then X, and anything that X causes, is non-rational.

But if all this is true, we have lost all grounds to suppose that anything that I've typed so far is rational. We'd be reduced to saying that we should just call it rational for pragmatic reasons. So, what would have to be the case for our arguments to have rationality or validity?

Lewis here introduces another relation - along with the cause and effect relation - called the ground/consequent relation. I assume this relation is a universal that is in time, but not in space (can't expound on that anymore right now), for I have other reasons for thinking that our minds - or more exactly our mental properties - are in time, but not in space. That is, these properties have no extention, and so they are spaceless; and yet we seem to be related to this relation, and so the only other dimension I know of is time. When we argue validly or rationally, our minds hook up with or link with this relation in another dimension - a rational dimension - which is sufficiently free from the causal nexus so as to be determined by what it knows. Since we defined being non-rational in terms of being a lump of matter governed by the law of causality, we can in turn define the rational in terms of being a lump of matter with mental properties which allow the brain to link with the relation of ground and consequent, residing in a non-spatial, temporal dimension, so as to be free of the causal nexus; for if it not free of such a nexus, it is determined by physical causality, which will make it non-rational.

If the mindless process of events driven on by causality determines a particular event to be, what other conclusion can we draw other than that the particular event is a non-rational, determined product of blind determinative processes which came about like the millionth domino falling after the first was pushed over?

If you are a naturalist, you have no ground to believe anything you say is rational.