Matthew J. Franck
Robert P. George
William J. Haun
David T. Koyzis
Robert T. Miller
James R. Rogers
Russell E. Saltzman
Julian Baggini has a intriguing interview with philosopher and theologian Richard Swinburne about the existence of the soul.
Here are some admittedly amateur thoughts on the matter:
How can there be intelligence without the ability to seize upon and be affected by abstract concepts? How can an immaterial, abstract concept affect, or be seized upon by, matter and energy alone – as in strictly natural thought processes? They can’t. The reason we can grasp them is because there is an immaterial element to our intellect: a rational soul.
Those who went before us were not stupid. Because they didn’t have our technology, we smile at their misinterpretation of things due to their perception of the material Universe not being as precise as ours. Yet they had the same intellectual capacity we do; it is foolish not take their collective wisdom and their understanding of reality into consideration. A traditional belief, like the idea of the existence of our supernatural, rational souls, became traditional because it rang true to many intelligent people who went before us.
Consider the thinking of one Gregory of Nyssa, who was born about A.D. 335:
“A definition of the soul is then given, for the sake of clearness in the succeeding discussion. It is a created, living, intellectual being, with the power, as long as it is provided with organs, of sensuous perception. For “the mind sees,” not the eye; take, for instance, the meaning of the phases of the moon. The objection that the “organic machine” of the body produces all thought is met by the instance of the water-organ. Such machines, if thought were really an attribute of matter, ought to build themselves spontaneously: whereas they are a direct proof of an invisible thinking power in man.”
The water-organ, an amazing musical instrument, was an example of the technology of his time. It couldn’t think any more than modern computers can or will ever be able to think. There is simply no configuration of matter and energy that enables them to grasp or be affected by the immaterial. Abstract concepts, the grasping of which is essential for intelligent thought to take place, are immaterial. We can think rationally, so there must be an immaterial component to our intellect that is able to interact with immaterial abstract concepts. It has traditionally been referred to as our rational soul.