The Inadequacy of Mechanistic Causation

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Jeffrey Thayne

Even if you can invent a purely mechanistic account of why you raise your hand to ask a question in a biology class, that account will never provide the complete picture.

Let’s imagine, for a moment, that you are in a biology class, learning about how life evolved through eons of evolution. You raise your hand to ask the professor a question. The professor asks, “Why did you raise your hand?” Naturally, you would respond, “Because I wanted to ask a question.”

The professor then said, “Hm, let me rephrase that–why did your hand rise into the air?” That’s a strange way to ask the question, but it is clear that he is asking a different question than the one you answered. He is looking for the causal mechanism that raised your hand into the air.

Let’s explore a possible answer to the question: Your hand moved into the air because certain muscles contracted in your arm, exerting enough force to counteract the force of gravity. Your muscle contracted because nerve signals from the brain sparked a chemical reaction in the muscle cells. Here’s where the question gets tough: why did your brain signal your arm muscles to contract?

“Well, because I wanted to ask a question,” you might respond. But to respond like this is to depart from the strictly mechanical and physical account we have been developing. Let’s speculate a little into the workings of the brain. Let’s suppose the nerve signals to your arms were in response to certain electric signals that triggered the portion of the brain that typically sends nerve signals to the arm. The signals that triggered this portion resulted from a pattern of electrical activity in the brain.

Some neuroscientists theorize that thought patterns have evolved over time as survival mechanisms.

These patterns are the result of two things: first, over the millennia, organisms developed with central nervous systems that could respond in complex ways to the surrounding environment. The reason these organisms developed was because organisms with the beginnings of such a nervous system had a higher survival rate than their peers amidst a harsh exterior environment. Naturally, there began to be more of them around. Also, those organisms that developed central nervous systems that could adapt their responses based upon how favorably their environment reacted to their responses also outlived their peers.

Second, these creatures found themselves in a certain environment that would react more favorably to their survival if they acted in certain ways, such as sending nerve signals to the arm (causing it to raise) prior to sending nerve signals to the mouth (causing it to speak) when in an environment the creatures labeled a “classroom.” One of these creatures is you. As a result of genetic adaptations and socio-cultural instruction, you raised your hand during your biology class.

The real picture may be much more complicated. Maybe, perhaps, a hundred times more complex, but that doesn’t change the fact that a purely scientific, mechanistic, or causal account of you raising your hand will be presented entirely in terms of the molecule interactions of inert matter, random variations of the gene pool, or a complex stimulus/response training.

What is the challenge with this? It is difficult to find room for agency in a purely mechanistic account of human behavior. At one point did the creature described above choose to raise its hand? Everything that happened, happened because of the inevitable interactions of inert matter or the inevitable result of stimulus/response training. If such an description is sufficient to account for you raising your hand, than any discussion of agency produces a redundant explanation; the event has already been explained, without resorting to ambiguous or non-understood constructs such as “agency.”

For these reasons, while I believe the language of naturalism and modern science are probably useful ways of conversing about many experiences we have in the world, I place no hope that we will be able to explain the world in that language alone. I believe that we live in a world that cannot be accounted for solely in terms of mechanical or physical processes. I believe that a discussion of agency is crucial to understanding this world, and if it is crucial, than no other account can be sufficient. The kind of agency I refer to is either by the Newtonian determinism of the modern era, or reduced to randomness by the ontological indeterminism of quantum mechanics.

For this reason, I propose that we see the mechanistic sciences as a useful tool for describing the physical world, but that we avoid the claim that they represent the reality of the physical world. This is because if agency is a real entity, it must be accounted for in different terms than are available in a purely mechanistic or causal description of the world. Also, if there are at least some events that cannot be explained mechanistically, then there is no real reason to insist that any event must be explained mechanistically, except that such a explanation is a useful descriptive tool (rather than the actual nature of things).

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