Logic and Mind: The Poverty of Adaptation and the Philosophy of Logic Naturalised

One often comes across many “just so stories” in the context of human evolution. One field that has, or perhaps had, almost turned this into an art form is evolutionary epistemology.

Take say the following just so story, typical of the genre, which is applicable to logic. We assume that the species possesses a “logic faculty” or “faculty of reason” of the mind. This faculty of reason would encompass what we call classical logic, most especially the principles upon which it is based such as the law of excluded middle.

The just stories have it that we acquired a faculty of reason because of its functional nature; such a faculty is highly adaptive, given that it leads to the formation of valid inferences, and so incurred upon Homo sapiens a most splendid evolutionary advantage denied other species.

In this sense our minds are furnished with tacit or innate knowledge of classical logic, which the conscious mind through inquiry by logicians subsequently formalises, because they lead to valid inferences about the world rather than because of the peculiar cognitive architecture of the mind.

I do not believe this position to be correct.

We know, of course, of non classical or alternative logics with rules of valid reasoning that reject the principles of classical logic. There is no reason why we should say, a priori as it were, that such systems of valid inference would not be adaptive, that is would lead to valid inferences about the world. It would be possible for a clever thinker to come up with an array of circumstances from our evolutionary past, that is just so stories precisely, that demonstrate the adaptive value of a non classical logic. Quantum logic serves as a case in point.

Let us call the faculty of reason “natural reason” or “natural logic” and alternative systems “formal reason” or “formal logic.” The faculty of reason based on classical logic has it scope and limits, as do non classical systems.

There are some problems that remain beyond the scope of the faculty of reason. There are some problems that remain beyond the scope of non classical systems. The cracking of a sub set of the set of problems that are beyond natural logic, but within the scope of formal logic, may confer upon a species that possesses a faculty of formal logic significant advantages of selection.

What this demonstrates, it seems to me, is that we possess a faculty of natural logic because of the cognitive architecture of the mind not some unique transcendental appeal to be conferred upon natural logic as opposed to formal logic.

In this sense the study of classical logic, and mind, would be a type of philosophy of logic naturalised that is the study of natural logic becomes a species of naturalistic inquiry in so much as the forms of valid reasoning are a natural kind.

Critical to such a naturalistic endeavour is understanding what is it about the cognitive architecture of the mind that provides us a faculty of natural as opposed to formal logic. Evolution by means of functional adaptation it cannot be. So, what is it? What is it about the way we process information that gives us natural logic as opposed to a formal logic?

I have no idea.

Perhaps experimental philosophy might be able to make some contributions here.

Notice also that there are other problems to the evolutionary view, such as the existence of cognitive biases that are, as Mr Spock had it, illogical.