The following is from Ronald Nash’s intro to presuppositional apologetics, Faith and Reason. Thanks to Joel Tay for transcribing the passage.
The Argument From Truth
Theists have more resources at their disposal than they often realize. One oft-neglected argument for God’s existence invites us to reflect about the ground of truth. So far as I know, this argument makes its first appearance in Book 2 of Augustine’s On the Freedom of the Will, written in A.D. 395. There is at least one clue that Thomas Aquinas thought the line of reasoning sound. Its tow major modern proponents appear to be Gordon H. Clark and Alvin Plantinga. Since Clark and Plantinga present different versions of the argument, that address audiences with somewhat different philosophical interests, I am going to look at the argument from both contemporary perspectives. This makes sense because it is sometimes easier to understand a difficult argument when approaching it from two different directions. While Clark’s presentation is simpler, it may puzzle readers who are unaccustomed to talking about truth apart from propositions, the carriers of truth. Plantinga’s version of the argument is more in tune with contemporary way in which philosophers typically think of truth.
Clark’s Version of the Argument
Gordon Clark’s account of the argument from truth utilizes six steps:
1. Truth Exists
2. Truth is immutable
3. Truth is eternal
4. Truth is mental
5. Truth is superior to the human mind
6. Truth is God
1. “Truth exists.” Clark establishes this point by reminding us of the self-defeating nature of any attempt to deny the existence of truth. Since skepticism is false, there must be knowledge; and if there is knowledge, there must exist the object of knowledge, namely truth.
2. “Truth is immutable.” It is impossible for truth to change. As Clark says, “Truth must be unchangeable. What is true today always has been and always will be true.” For Clark, all true propositions are eternal and immutable truths. He has no use for pragmatic views of truth that imply that what is true today may be false tomorrow. If truth changes, then pragmatism will be false tomorrow-if, indeed, it could ever be true. Truth itself is unaffected by the fact that sentences like “I am now typing” are sometimes true and usually false. Since I’ll present a rather long argument in defense of this claim later in this chapter, I’ll assume that this possible problem can be answered and move on to Clark’s next point.
3. “Truth is eternal.” It would be self-contradictory to deny the eternity of truth. If the world will never cease to exist, it is true that the world will never cease to exist. If the world will someday perish, then that is true. But truth itself will abide even though every created thing should perish. But suppose someone asks, “what if truth itself should perish?” Then it would still be true that truth had perished. Any denial of the eternity of truth turns out to be an affirmation of its eternity.
4. “Truth is Mental.” The existence of truth presupposes the existence of minds. “Without a mind, truth could not exist. The object of knowledge is a proposition, a meaning, a significance; it is a thought.” For Clark, the existence of truth is incompatible with any materialistic view of man. If the materialist admits the existence of consciousness at all, he regards it as an effect and not a cause. For a materialist, thoughts are always the result of bodily changes. This materialism implies that all thinking, including logical reasoning, is merely the result of mechanical necessity. But bodily changes can be neither true nor false. One set of physical motions cannot be truer than another. Therefore, if there is no mind, there can be no truth; and if there is no truth, materialism cannot be true. Likewise, if there is no mind, there can be no such thing as logical reasoning from which it follows that no materialist can possible provide a valid argument for his position. No reason can possibly be given to justify an acceptance of materialism. Hence, for Clark, any denial of the mental nature of truth is self-stultifying. In Clarks words,
“If a truth, a proposition, or a thought were some physical motion in the brain, no two persons could have the same thought. A physical motion is a fleeting event numerically distinct from every other. Two persons cannot have the same motion, nor can one person have it twice. If this is what thought were, memory and communication would be impossible…It is a peculiarity of mind and not of body that the past can be made present. Accordingly, if one may think the same thought twice, truth must be mental or spiritual. Not only does [truth] defy time; it defies space as well, for if communication is to be possible, the identical truth must be in two minds at once. If, in opposition, anyone wished to deny that an immaterial idea can exist in two minds at once, his denial must be conceived to exist in his own mind only; and since it has not registered in any other mind, it does not occur to us to refute it.”
To summarize Clark’s argument thus far, truth exists and is both eternal and immutable. Furthermore, truth can exist only in some mind.
5. “Truth is superior to the human mind.” By this, Clark means that by its very nature, truth cannot be subjective and individualistic. Humans know certain truths that are not only necessary but universal. While these truths are immutable, the human mind is changeable. Even though beliefs vary from one person to another, truth itself cannot change. Moreover, the human mind does not stand in judgment of truth: rather truth judges our reason. While we often judge other human minds (as when we say, for example, that someone’s mind is not a keen as it should be), we do not judge truth. If truth and the human mind were equal, truth could not be eternal and immutable since the human mind is finite, mutable, and subject to error. Therefore, truth must transcend human reason; truth must be superior to any individual human mind as well as to the sum total of human minds. From this it follows that there must be a mind higher than the human mind in which truth resides.
6. “Truth is God.” There must be an ontological ground for truth. But the ground of truth cannot be anything perishable or contingent. Since truth is eternal and immutable, it must exist in an eternal Mind. And since only God possesses these attributes, God must be truth.
“Is all this any more than the assertion that there is an eternal, immutable Mind, as Supreme Reason, a personal, living God? The truths or propositions that may be known are the thoughts of God, the eternal thoughts of God. And insofar as man knows anything he is in contact with God’s mind. Since further, God’s mind is God, we may… say, we have a vision of God.”
Therefore, When human beings know truth, we also know something of God’s nature. There is a sense in which all knowledge is a knowledge of God.
-Ronald Nash, Faith and Reason, p. 161 – 164
* For Clark’s argument see A Christian View of Men and Things