Let’s consider truth. Truth in the abstract. The concept of truth. Why does it matter to us?
To be clear, the question is not whether particular things are true or not, or whether we prefer truth to falsity, or even our affinity for truth as opposed to falsehood in ourselves or others. The question is: Why do we order our thinking according to this one criterion? Why do we constantly make distinctions between what is true and what is not? Why do we engage propositions primarily on the basis of their truth or untruth? Why do we consider the God proposition according to whether it is true or not? Why do we conduct investigations of reality on the basis of what is true and what is not? Why is it that whenever we engage in any scientific inquiry, we do so for the purpose of finding what is true about our physical environment? The entire project of science would be utterly meaningless without this orientation to truth.
Even attempting to isolate truth as an orientation takes some effort. That orientation is so ingrained and so instinctual that it is difficult to take ourselves out of our own minds, so to speak, in order to look back in and identify this hard-wired basis for thinking. When we talk about having an orientation toward truth, we are saying that it is true that we are oriented to truth. So natural does this orientation seem, that it is difficult to conceive how one might think, if not by the criterion of truth.
But if we are to understand reality if there is no God, then we must conceive it. We must because if there is no God, then all of reality, including the truth orientation, must be explained as the consequence of matter in motion. But matter in motion cannot explain this orientation.
Let me explain, first by contrasting the theist explanation. We expect someone to tell the truth because we generally expect (unless shown otherwise) that the person shares our belief in the ethical or moral principle of truth. A principle such as “truth” is by its nature intangible, conceptual, eternal, and grounded in the mind, not the brain. We implicitly draw on the principle that truth is preferable to falsity, when we aspire to speak truthfully, and when we accord to someone else the presumption that they speak truthfully.
But should that presumption apply, when a materialist declares that materialism (or anything else) is true? Does it make sense in this situation to assume a shared principle that truth is preferable to falsehood? Materialism is the belief that there is no supernatural reality; that the only reality available to us is physical. What that means is that a person is a body, only; that his thoughts are the result of a particular combination of physical conditions in the brain, and nothing more. The mind has no supernatural component, in this worldview. The mind and the brain are the same thing. Because of this, materialists must hold to some form of determinism; that is, that a given action (say, my writing this, or your reading it) is the necessary result of all the past movements of matter in space and time. Further, that actions at this moment are determined by the particular movement of every atom, from the beginning of existence down to the present instant. Obviously a particular action is influenced more by some vectors than by others. But the action is pre-determined by physical reality, materialists must hold. This physical determinism would apply to everything, including what a person says (or writes) on a given occasion. So when a materialist says that materialism is true, why believe him? The thoughts he entertains are the result of the body’s reaction to all the stimuli that preceded, not some external, objective truth.
The materialist response might be that we are evolved to be truthful, but that doesn’t work. Obviously people tell lies all the time, or shade the truth, or are mistaken. Moreover, evolution means self-selection for fitness, not truthfulness. While fitness may be enhanced by telling truth on some occasions, it is enhanced on other occasions by telling lies, or by repeating mistaken beliefs as if they were true. At most, the materialist can posit a general tendency of human organisms to tell the truth because truthfulness is usually advantageous to the species. But not because truth is a worthy ideal in and of itself. If our actions are determined by physics alone, there is no assurance of truth-telling (or -thinking) on any particular occasion. The determinant for the content of speech is not truth, but the complex vectors comprising the speaker’s existence at the moment of the utterance.
The point is that truth in the abstract is not a criterion for our thinking true or false things, if materialism be true. The criterion is survival advantage. The result may coincide with what you and I think of as objective truth, but it may not. If survival advantage leads to thinking things that are not true, then falsehood prevails in our thinking.
Even having this discussion would be difficult (that is, if the materialist explanation of reality were valid) because we would on the one hand speak of “truth” as a word attached to a thought that is deterministically generated on the basis of natural selection, but on the other hand speak of “truth” in the usual way – as a word to describe something always and everywhere and objectively true; true regardless of our thoughts about it. So the words “true” and “truth” would confusingly have two distinct meanings, and to carry on the discussion, we have to confusingly shift between them.
Suppose we try to solve that problem. Suppose that we call truth “truth,” but we call the beliefs generated by materialistic, deterministic, evolutionary thinking something else. Let’s call it “Fred.” If matter in motion is all of reality, we have an orientation to Fred, not to truth. Natural selection may cause Fred to coincide with truth, but not necessarily, and if it did we wouldn’t know it because there is no “truth,” only Fred. If false ideas better serve the end of natural selection, then Fred will not be truth.
We don’t have to go far to find an example of this. Materialists say there is no God. That’s what materialism is. But obviously, many people believe in God. If we imagine consistent materialist thinking, it must be because God is Fred. It serves our impulse to survive and procreate, because religion enhances social living, which in turn enhances survivability. And the God element of religion originated because our heightened fear of possible predators causes us to believe in things that aren’t true, if doing so enhances our survival prospects. If we imagine there is a lion in the bushes waiting to eat us, we avoid the bushes and live. We come to believe there is a lion whether there is one or not, because we are more apt to survive. The lion is God is Fred.
The irony in the materialist trope concerning the God proposition is that the explanation for the putatively false God belief – natural selection – would mean that we believe Fred, not truth. And God is Fred. The false God proposition itself would prove the Fredfulness but untruthfulness of materialism. If materialism is the explanation for reality, then it is meaningless to talk in terms of true and false.
What this means is that if we’re to be good materialists, we have only two ways we can go. We can either abandon the concept of truth, in which event we should stop using the word and the concept that goes with it, or we can abandon materialism, on the grounds that the orientation to truth cannot be abandoned. Whether the orientation to truth can be abandoned or not is the next subject to which we turn.
It is difficult even to conceive how we might think without the binary tool of truth/untruth. In fact, it is so difficult to conceive (“conceiving” being an exercise of the mind) that we should ask whether the truth orientation is so basic to our belief system that it cannot be abandoned. Descartes famously said “cogito ergo sum” (I think therefore I am) and from this philosophers often begin their treatment of epistemology – how we can know anything – with the proposition that a person’s mental processes are “basic.” So basic that we can accept as true that what presents to our sense impressions are real. We’re not all brains in jars, thinking that we’re experiencing these things.
Some argue that the felt presence of God, the sensus divinitatis, is similarly basic. Whether it is or not, it is difficult to argue that the orientation to truth (and not Fred) is not basic. It is clear that we could not function at all, much less survive in a hostile and truth-oriented world, if we did not have this truth orientation as a fundamental element of our being. In order to understand what is real, we do not first have to grapple with whether at a particular moment we are oriented to truth, rather than to, say, Fred. The orientation to truth is basic. The orientation to Fred is not. Materialists might hypothesize that Fred tends to coincide with truth, but even the hypothesis assumes a truth. Materialism cannot explain the orientation to truth. But it is explained by the existence of a God who brought this element of order to His universe.
And I apologize if your name is Fred.
 To be sure, many materialists will differ with the notion of absolute determinism, and there are variations on the theme of determinism, philosophically. But ultimately, materialism begets determinism.
 As with truth in the abstract, so with rationality. It may be to evolutionary advantage to reason and to reason logically, but obviously that is a hit or miss proposition. The most dyed-in-the-wool materialist empiricist would agree that scientific observation and experimentation sometimes yields error, in which event the empirical process corrects itself. Indeed, that is a boast of those who rely on empiricism alone for truth.
 Aristotle, Aquinas, Calvin, and contemporarily, Alvin Plantinga