by Albrecht Moritz
(2010, revised June 2012)

Naturalism is the view that nothing exists beyond the natural world and that only physical laws operate in our world, i.e. that also humans are purely physical beings. Let us suppose the naturalist wants to defend the position that naturalism is true.

Yet under naturalism every thought, just like everything else, is physically determined. Some propose that freedom of thought might be a result of 'emerging complexity', but this is based on a misunderstanding of the concept. While emergence results in phenomena that could not be predicted from the basic components of the system on their own, it never violates the physical laws by which these basic components operate. Such a violation would have to occur if free thought could be the result of purely physical processes, which are either deterministic or, at the quantum level, random on a probabilistic basis (yet significant quantum level influence on thought is not feasible under naturalism, since it would just produce random thoughts).

The physical determination of thought under naturalism of course includes the thought "Naturalism is true". Therefore, when making the claim, the naturalist has no free choice but is at the mercy of the circuits in his/her brain to judge on the question.

These circuits were shaped by evolution – yet evolution is of no help to reliably arrive at the claim that naturalism is true. Already Darwin recognized the problem that natural selection may not suffice to explain the human mind's capacity for recognition of truth and objective thought – evolution selects only for physical adaptation and behavior, not for correctness of beliefs ^*). When evolutionary scientists claim that religion was selected for its behavioral survival advantage, they in fact concede, if they adhere to a naturalistic worldview, that evolution can indirectly select for an allegedly false belief. So there is no use in saying that, in terms of frameworks of beliefs, evolution probably has endowed us with a reliable ability to see that naturalism – an abstract concept far beyond everyday sensory experiences – is true, and therefore we ‘ought’ to see the truth of naturalism even under determinism.

*) Let me be clear from the onset towards those who believe this turns into yet another anti-evolution argument: I fully subscribe to the science of evolution and reject the idea of biological so-called Intelligent Design. I even have written a review article on the origin of life by natural causes for the evolution website Talkorigins.org. Yet evolution is a physical, material process, and the question that this article addresses is whether rationality and recognition of truth are possible as a purely physical phenomenon, or if the human mind requires, in addition to the brain, a component that allows it to transcend physical determinism.

Certainly the naturalist might still claim that evolution has endowed the human brain with basic and universal logical circuitry, shaped by its survival value, that reliably can decide "if we just give the issues some thought". However, even if evolution could accomplish the creation of reliable logical circuitry (which is debatable), an informed decision for or against naturalism is not solely a matter of simple and straightforward logic based on premises that should be self-evident to everyone, independent of the angle from which they are looked at. Rather, when the issues are thoroughly studied and well thought through, it is a matter of careful weighing of (giving weight to) and interpreting abstract and rather complex evidence and arguments pro and con, and this goes far beyond basic circuitry that might have been induced by evolution for its survival value. So there cannot be an evolutionary ‘ought’ on this issue after all.

Thus, given all the above, it cannot rationally be claimed that evolution has shaped our brain circuits in such a way that they are bound to reliably settle the particular question at hand, "when engaged properly". This, however, would be the only way to guarantee the right outcome under naturalistic determinism. (For theists there is no problem here; they usually view the brain as an integral part of the mind, on which the mind fully depends for its functioning, but they do not view it as identical to the mind – evolution then does not fulfill as ultimate a role in shaping the functioning of the mind as it does for the naturalist.)

How then can the naturalist nonetheless assert that naturalism is true and its acceptance rational? S/he considered the evidence, s/he will reply. Yet under naturalism the brain determines how to interpret the evidence – you have no say in that. So the naturalist's brain determined that naturalism is true, and mine determined, considering the evidence as well, that naturalism is not true. Now, which brain is right? If the naturalist's acceptance of naturalism is solely dependent on the firing of his/her neurons over which s/he has no control (under determinism), then it is not possible for him/her to know that his/her brain is right and that naturalism is true. Thus under naturalism the claim that naturalism is true becomes incoherent and self-contradictory. Naturalism defeats itself.

A humbler position might be taken. The naturalist can simply hold that naturalism is a useful 'working hypothesis', with no truth claim attached. However, given the issues discussed above, how can the naturalist even know that this working hypothesis makes sense and is rational? Or if s/he does not claim to know if it is useful and valid, then how can s/he at least be rationally convinced that it is? The problem persists. Also as a mere working hypothesis, naturalism defeats itself.

***

All this leads us to a related issue: In general you can only rationally believe that something is true if in fact (not just as an illusion) you can claim intellectual responsibility for your thoughts and if you can take ownership of the judgment of what is rational and your choice in favor of it. In other words, if you are not solely dependent on the firing of the neurons in your brain over which you have no control, and for which you cannot assume responsibility. Such freedom is not possible under determinism, which is entailed by naturalism. Yet we know that we are a rational species and that this leads to reliable results – in fact, the entire human enterprise of science and technology is built on the foundation of rationality – and from this knowledge it follows that naturalism is necessarily false.

Certainly, the essential connection between rationality and genuine freedom in rational judgment, which is not possible under determinism, may be objected to on several grounds. Let us examine them.

Some may claim that our brain, shaped by evolution, judges what is rational just fine even without our choice and we are just aware of the result of that judgment. But then the question arises: how could we judge that judgment to be right under determinism? That follow-up judgment would be just another decision made by our brain which we could not judge ourselves. If we could not do that, we could not know that our brain made a rational judgment, and without that knowledge we could not be rational.

This might be countered with the following: our brain knows from experience that this or that kind of rational judgment will yield good practical results, and this experience is a sufficient judge for our brain to know that a related thought process is rational, even if we ourselves do not perform the judgment freely, but our brain does so in a deterministic way. Yet this argument is inadequate: also in areas where we do not have any prior experience we can know that, given the premises we work with, certain rational judgments are true even before we see verifiable results from them – since this also holds for complex and abstract thought processes, an explanation by basic circuitry induced by evolution for its survival value falls flat. While we are aware of this phenomenon from our own thought processes, it is exemplified in a particularly impressive manner in Einstein’s famous theory of general relativity. When Einstein published it, he knew that it had to be right if his premises were right, even though it was counterintuitive, unrelated to prior human experience, and would radically change our views of the physical world. Obviously, we also know that observation confirmed the theory.

There may also be those who hold that individual judgment plays a limited role for the greater goal of the rational enterprise. For example, the claim may be made that rationality in science is based on consensus. Yet precisely the opposite is true, as I also can attest from my own experience as a scientist. As Thomas Nagel writes in his excellent book The Last Word ^*), a convincing defense of objectivity of rational thought: "In most cases we will then conclude that reason and objectivity are not grounded in consensus, but on the contrary, that where consensus is available, it arises from the convergence among different individuals, all reasoning to get at the truth." Again, Einstein’s example makes this perfectly clear – he alone developed the theory, and consensus arose among the scientific community after considering the concept and the subsequent evidence as it became available.

The weight of individual rational judgment is also not substantially diminished by the objection that progress in science is a result of endless trial and error. Yes, that is the case, but mainly because observation and experiment show that certain, often previously unknown, parameters were not taken into account, or that some of our ideas about how the world works were fundamentally flawed (e.g., at a time where quantum mechanics was not yet known). Trial and error in science are much less often the result of flaws in the rational process itself.

Finally, referring to computers as an example of deterministic matter capable of exhibiting ‘rational thought’ is not a valid counterargument either. The functioning of computers is dependent on human rationality – even if they are induced to 'learn' and in the process to create output 'on their own' – since they are programmed by humans according to the rules of logic and reason that these apply. Instead of being programmed to calculate 9 x 7 = 63, a computer could just as easily be programmed to calculate 9 x 7 = 126, also obeying the laws of physics. It would not know the difference.

This also points to another distinction between us and computers: we can verify our rational processes, a computer cannot. This ability to check and control our thought processes and cognitive biases in a self-reflective manner further indicates that our rational judgment is a genuinely free choice, at some level of independence from the firing of neurons in our brain that we cannot control. Certainly, a computer can be programmed to monitor the technical functioning of its circuitry, but this is a different issue: it cannot monitor if its functioning gives correct results in the first place. This is up to the human designers and programmers. More generally, a computer does not understand what it is doing, only its human designers and programmers do, and the usefulness and interpretation of its output is wholly dependent on its human users.

In conclusion, none of the arguments against the essential connection between rationality and genuine freedom in rational judgment are valid. The human mind must have a component that is not subject to physical determinism, i.e. it must have an immaterial component. This indicates that the religious notion of a 'rational soul' is correct.

That rational thinking must be free, independent of physical determinism, is also supported by the consideration that ground and consequent in thinking are different from, and must stand outside the pattern of, [physical] cause and effect (again, that they coincide in the working of computers is not a valid counterargument, see above).

There is an excellent article by C.S. Lewis about this topic, "The Cardinal Difficulty of Naturalism". Here is an excerpt:

The remainder of the article is just as hard-hitting, yet also rich in subtlety of argumentation. It may take some time to fully understand it all in detail (it certainly took me a while before it all sank in), and I have seen attempts at rebuttal of it on the web that did not at all understand what they aimed to refute, and completely missed the point. – Lewis's ponderings of quantum mechanics at the beginning of his article can be safely ignored, he does not use them in his argument anyway.

***

Yet many will say: how can one believe that the mind is more than just the brain, given the findings of neuroscience that mental activity precisely and in detail correlates with brain activity? However, correlation does not automatically imply causation. Furthermore, and importantly, this correlation was fully predicted and expected by classical Aristotelian-Thomistic philosophy, since immaterial conceptual thoughts always need to be accompanied by mental images, which are material and provided by the brain. For this, see Edward Feser, Against Neurobabble (link), Modern biology and original sin, Part I, subheading What is man? (link) and the last few paragraphs of a follow-up article on the latter, Monkey in your soul? (link). These articles provide an additional, essential argument for the immateriality of thinking.