This is last part of my essay on free will.
This brings me to two arguments against the idea of a “soul”. The first argument is that the soul is a so-called “God of the Gaps”. A “God of the Gaps” is any supernatural explanation that is offered on the basis that no natural explanation is currently known. In other words, it attempts to fill a gap in our knowledge by plugging it with a supernatural explanation. This approach is unjustified: not only are supernatural explanations generally untestable and unsupported by the evidence, but they require far-fetched assumptions to be made (such as the existence and nature of a deity), thereby violating the principle of Occam’s Razor. Supernatural explanations, then, are premature until all natural theories can be properly ruled out.
Astronomy has frequently been the target of god-of-the-gap arguments. Almost all astronomical observations, starting with simple phenomena such as the movement of the sun across the sky, have, at first, been attributed to the work of a god (or gods). One by one, though, these arguments have been refuted by empirically established scientific theories. Today, the remaining gaps in astronomy are few and far between. The most popular is the idea that a god created the universe, since scientists have yet to agree on, and verify, a natural explanation for the Big Bang.
I suggest that the soul is a god-of-the-gaps argument because it was offered as a supernatural explanation for human behavior before we began to understand the natural functioning of the brain. Indeed, without any knowledge of the different components of the brain, and how they work together to produce consciousness, it is very easy to see how the idea of the soul arose: superficially, our behavior appears to be far beyond the abilities of the rather drab grey organ that occupies our skulls, especially considering the vastly more mundane functions of similar-looking organs elsewhere in our bodies. The soul thus appears to be a good first guess for how we behave the way we do. However, we have started to understand the brain now, and everything we have seen points to an extraordinarily complex organ capable of carrying out all the functions required to produce human behavior. One experiment after another has shown that interference with, or damage to, different parts of the brain can influence every aspect of our behavior, including our sensory abilities, cognition, and even moral attitudes. Coupled with the apparent evolutionary development of brains, these discoveries lead firmly to the idea that no soul is required to explain human behavior. The gap for supernatural explanations has essentially shrunk to nothing. It is no surprise, of course, that the final frontiers of scientific exploration, including brain science and cosmology, have also been the final refuges of god-of-the-gap arguments. Only where questions are yet unanswered can supernatural conjecture thrive.
The second argument against the idea of the soul is that it is poorly defined. No proponent of the soul has ever satisfactorily answered questions about what it is made of, how it works, whether animals have them, etc. Indeed, the soul is not usually given any definition at all: it is simply taken for granted as some ethereal, invisible entity that exists independently of the body it inhabits. The only specificity usually offered about the soul is that, unsurprisingly, it resides in the brain. This realization has come about by the simple, if macabre, process of elimination: people who have lost their limbs, or have had various internal organs removed or replaced, suffer no consistent loss of, or change in, personality. Amputees and transplant patients do not generally lose their ability to make decisions, either. The only organ which, if damaged, appears to influence personality and decision-making, is the brain. It is astonishing that these realizations have not led to a more widespread rejection of the soul hypothesis. If an invisible, ill-defined entity once thought to be responsible for our thoughts is found to reside in the one bodily organ that has a very real, proven physiological capacity for producing thoughts, surely it is obvious that the bodily organ is producing the thoughts, and that the invisible, vaguely defined entity is simply an illusion?
Imagine going back to a time when it was not understood how humans were able to hear. We might easily have thought that such a wonderful gift couldn’t possibly have a mundane physical explanation, that there must be some kind of spirit that made us aware of the sounds around us. Then, some time later, we would have discovered that we had small, very delicate mechanical systems within our heads that responded to sound waves. Should we then have concluded that our invisible hearing spirit resided in the small bones of the inner ear, or should we have concluded, as we indeed did, that the aural mechanism itself was sufficient to capture sound? The latter seems to be the only sensible conclusion, and so it is with the brain: we have discovered an organ that is known to influence every type of human thought and behavior – why then should we cling to the idea that an invisible, ill-defined entity is necessary to explain these things?
The following people and resources were invaluable to my formulation of this essay:
Ben Best, http://www.benbest.com/philo/freewill.html.
Gary Cziko, “Without Miracles”, MIT Press, Cambridge, Massachusetts, 1995 (http://faculty.ed.uiuc.edu/g-cziko/wm/05.html#Heading2).
Reasonable Doubts podcast: “RD Extra: Jeremy on the Don Johnson Radio Show”, June 7, 2010 (http://doubtreligion.blogspot.com/2010/06/rd-extra-jeremy-on-don-johnson-radio.html).