So, here we go with a little bit of philosophy. I recently ran across this argument and thought experiment in the book, “In Defense of Miracles: A Comprehensive Case for God’s Actions in History.”
For a little bit of background, this argument is in the tradition of a category of arguments sometimes called “arguments from reason” and is intended to buttress the basic idea that we live in a universe where minds and other non-natural properties/agents exist. More specifically, it argues for the inadequacy of Naturalism to account for reason-both the reasoning process and the application of reason to reality.
C.S. Lewis actually brought the argument from reason to the forefront in his book “Miracles” by stating that the process of reason is itself non-natural, and therefore an indication that nature is not all there is. The following argument and thought experiment is an explication of that basic thought. (The thought experiment belongs to someone else, so be warned- because I have not read his original work what follows it is all my fault.)
Imagine yourself on a train as you see an arrangement of white rocks on the side of a hill which reads, “Welcome to Wales.” At this point we can work with two assumptions. First, we can assume that someone intentionally arranged the white rocks on a hillside adjoining Wales. Given this assumption, we can safely conclude that we are actually entering Wales. We can make this conclusion because we have the conjunction of the message and the belief that it was formed by an intentional, non-deceptive agent.
Secondly we can assume that the rocks are an arrangement of a natural, non-agent directed process (this includes everything from rocks rolling downhill to humans lacking non-natural agency). Given this scenario, we cannot take it to be that we are entering Wales. The rocks could have formed the words in Denmark. No meaning, no conveyance of truth, can be taken from a random assortment of rocks anyway. Additionally, we have lost the conjunction we had in the first assumption. We no longer have a meaningful message produced by a non-deceptive, intentional agent. Even if a human formed the rocks, if we assume Naturalism to be true, the human was simply caused by prior natural causes to form the rocks where they did. In order to convey the true statement, “Welcome to Wales,” the rocks have to be placed in the right place with intent. Only then are we justified in believing the message in the rocks. Additionally, as the argument goes, intent is not a natural property.
This last point, about the human forming the rocks by natural processes, might be a little sticky for some so let me explain a bit. If a human is nothing but a collection of atoms and molecules, the actions engaged in by those molecules can be explained entirely in physical terms. In other words, other molecules and natural processes cause molecules to do things. Given the truth of this, this kind of human arranging rocks on a hillside is no different than a string of dominoes falling. If a hundred topple over and a few in the middle are white, then there is nothing to be made of the white dominoes other than they fell just like the others. There is no rhyme or reason to whether they were the first 7 or numbers 33-45. There is no intent or reason involved with the white dominoes.
The import of this argument and the thought experiment is that reason and truth can only be conveyed if non-natural properties/persons exist. If God does not exist and we do not have minds (non-natural parts to our personhood), then reason and truth cannot exist. The fact that we do reason and do have a grasp of the notion of truth indicates that there is more to the universe than just the natural.