Subdividing the AFR

I. Subdividing the Argument
One aspect of my own discussion of the argument that has, I think, influenced the discussion of the argument the most is my subdivision of the argument from reason into six subarguments. In examining the argument I found that the argument focused on different elements of the reasoning process, and that one could find difficulties for naturalism at more than one step along the way.
Perhaps Lewis himself also noticed that there are different elements to the process of rational inference. Consider this description of inference, which, interestingly enough, occurs in a critique of pacifism, not in a presentation of the argument from reason:
Now any concrete train of reasoning involves three elements: Firstly, there is the reception of facts to reason about. These facts are received either from our own senses, or from the report of other minds; that is, either experience or authority supplies us with our material. But each man’s experience is so limited that the second source is the more usual; of every hundred facts upon which to reason, ninety-nine depend on authority. Secondly, there is the direct, simple act of the mind perceiving self-evident truth, as when we see that if A and B both equal C, then they equal each other. This act I call intuition. Thirdly, there is an art or skill of arranging the facts so as to yield a series of such intuitions, which linked together produce, a proof of the truth of the propositions we are considering. This in a geometrical proof each step is seen by intuition, and to fail to see it is to be not a bad geometrician but an idiot. The skill comes in arranging the material into a series of intuitable “steps”. Failure to do this does not mean idiocy, but only lack of ingenuity or invention. Failure to follow it need not mean idiocy, but either inattention or a defect of memory which forbids us to hold all the intuitions together.”4
So Lewis isolates three steps in the reasoning process: 1) The reception of facts to think about, 2) The perception of a self-evident truth of rule that permits the inference, and 3) Arranging the fact to prove a conclusion. Sometimes in developing the argument from reason, advocates point out the difficulty the naturalist has in giving an account of how it is a thought can be about something. This aspect of thought, which philosophers since Brentano have called intentionality, has often been thought to be profoundly problematic for the philosophical naturalist. The next step in the process seems problematic as well, How is that that purely natural creatures completely embedded in the space-time continuum, could possibly not only know something that is true, but also must be true. Our physical senses might perceive what is, but how could physical beings know what aspects of what they experienced could not be otherwise? And then, finally what happens when we arrange statements to prove a conclusion? It seems that our understanding of the propositional content of one statement has to be the deciding factor in our being able to conclude the conclusion. As Lewis asked in his revised chapter, “Even if grounds do exist, what exactly have the got to do with the actual occurrence of belief as a psychological event?” Hence it looks as if the naturalist, in order to affirm the existence of rational inference, must accept the existence of mental causation in which the state of accepting the content of one statements causes the acceptance of the content of another statement. But how mental causation can fit into a naturalistic world has been widely regarded as a problem
In order to keep the strands of the argument straight, I divided the argument from reason into the following six subarguments:
(1) The argument from intentionality.
(2) The argument from truth.
(3) The argument from mental causation in virtue of propositional content.
(4) The argument from the psychological relevance of logical laws.
(5) The argument from the unity of consciousness.
(6) The argument from the reliability of our rational faculties.
I will analyze each of these arguments in turn.