by John M. Frame
This article was originally published in Kevin Vanhoozer, ed., Dictionary for the Theological Interpretation of the Bible (Grand Rapids: Baker Book House, 2005), 462-464. This is copyrighted material, used by permission of Baker Academic, a division of Baker Publishing Group, copyright © 2005. All rights to this material are reserved. Materials are not to be distributed to other web locations for retrieval, published in other media, or mirrored at other sites without written permission from Baker Publishing Group. Baker’s URL is http://www.bakerbooks.com, and the URL for the Baker Publishing Group is http://www.BakerPublishingGroup.com.
Logic is concerned primarily with (1) validity of arguments and (2) consistency of propositions. A valid argument is one in which, if the premises are true, the conclusion cannot fail to be true. Two propositions (factual assertions) are consistent if they can both be true at the same time. The science of logic seeks to understand what it is that makes arguments valid or invalid and what makes propositions consistent or inconsistent.
In the study of any text including Scripture, logic is an important hermeneutical tool. If a text says that all men are mortal, and Socrates is a man, then we may infer validly from that text that Socrates is mortal. In a sense, the text asserts, not only that all men are mortal and Socrates is a man, but also that Socrates is mortal. The conclusion is implicit in the text, and the logical argument makes that conclusion explicit. Logic, then, is a way of understanding the meaning of texts. So the Westminster Confession of Faith (1.6) locates the “whole counsel of God” not only in those things that are “expressly set down in Scripture,” but also in those things that “by good and necessary consequence may be deduced from Scripture.”
Human beings have been thinking logically (validly, consistently) since creation. The science of logic, the formal study of logical thought, was largely invented by Aristotle, and has continued through the work of such figures as Occam, Leibniz, Bertrand Russell, and Willard Quine. Sometimes logical theorists have tried to teach logic as a formal system analogous to Euclid’s geometry. But these systems have their limitations. For one thing, they deal only with propositions expressed in language. But human beings draw inferences, not only from language, but also from states of affairs. If I keep my car keys only in three places, A, B, and C, and I see they are not in locations A and B, I infer they must be at location C. That is logical reasoning, but I may never think to express it in a syllogism, or even in language. Psychologically, it may be nothing more than a feeling that impels me from one location to another. Logical thought, therefore (I am tempted to say “logical feeling”) precedes logical syllogisms, arguments, and systems. And we have no reason to assume that systems of logic today are rich enough to account for all the logical thinking that goes through our minds.
Does Scripture itself warrant logic? It does not contain or recommend any particular system of logic, but it does contain logical language, representing logical thought. Further, it recommends consistency and validity as virtues. When James tells us not only to hear God’s word but also to do it (James 1:22-25), he is recommending consistency between our professed beliefs and our actions. When Scripture tells us not to steal, but we steal anyway, we are not permitted to excuse ourselves by renouncing the virtue of consistency. God himself proclaims that his actions are consistent with his promises and threats. When someone claims to be a prophet of God, but events occur that are inconsistent with his prophecies, these events expose the claimant as presumptuous (Deut. 18:15-22). God does not lie or deny himself (2 Tim. 2:13, Tit. 1:2). Biblical prohibitions of false witness (Ex. 20:16, Eph. 4:25) emphasize the antithesis between true and false language and the responsibility of God’s people to speak consistently with the truth. Passages in which God evidently approves of untruth (as Ex. 1:15-21, Josh. 2:4-6, Heb. 11:31, James 2:25, Josh 8:3-8, etc.) are exceptions that prove the rule: Deception of the wicked (not the “neighbor” of Ex. 20:16) in these cases maintains consistency with the purposes of God and the sanctity of human life. Certainly none of these passages says anything to discourage logical thought and action.
As for inference, we should note that Scripture is often argumentative. It not only states the truth, but it also presents reasons for believing it and acting on it. Don’t worship idols, God says through Moses, because the Lord is jealous (Ex. 20:5-6) and because God chose not to reveal his form when he met with Israel on Mount Sinai (Deut. 4:15). Paul tells the Colossians that they should seek the things that are above, because they are risen with Christ (Col. 3:1), that they should present their bodies as living sacrifices because of the “mercies of God” (Rom. 12:1). So Scripture presents not only authoritative truths, but also authoritative logical inferences. It is not enough to seek the things that are above; we must seek those things for a particular reason, namely because we have been raised with Christ. So Paul endorses the syllogism: Those raised with Christ should seek the things that are above. The Colossian believers are raised with Christ. Therefore, they should seek the things above.
Logic, therefore, is a valuable tool for theology, a way of extracting meaning from Scripture and applying Scripture to human life. Indeed, one way to look at theological hermeneutics in general is to see it as a group of methods by which we derive logical implications from biblical texts. An interpretation of Scripture is never a mere repetition of Scripture. An interpretation always uses some words different from the biblical text. But the claim of an interpreter is, in effect, that his interpretation is an expression of meaning that is logically implicit in the text itself.
If the work of logic in interpretation is done well, the result will preserve the truth of the original text. A valid logical inference from Scripture will be as true as the texts that form the premises of that inference. So the Westminster Confession, as we have seen, locates divine authority both in the express words of Scripture and from truth deduced from Scripture by “good and necessary consequence.” One is almost inclined to think that one could greatly enlarge the biblical canon, simply by producing logical inferences from the current canon.
But it is not that easy. There are limitations and dangers in logical inference, sufficient to make it clear that such ambitions to enlarge the canon are mere fantasies:
1. First, although logic itself preserves truth, human users of logic are fallible. Logic preserves truth only when it is done right. But theologians and exegetes make mistakes in their efforts to reason logically. So believers in the infallibility of Scripture must make a sharp distinction between the authority of the biblical texts and that of post-canonical theology. Logical inference ideally preserves the truth of premises in its conclusions; but such inference as it is actually practiced does not necessarily preserve truth. That limitation, of course, pertains to all methods of interpretation. In this respect, logic is no different from textual criticism, translation, paraphrase, commentary, or theological analysis.
2. The fallibility of the practice of logic extends also to logical systems. Like all sciences, the science of logic has a history. Aristotle’s system of logic is different at points from those of Occam, Russell, and Quine, and it sometimes generates different inferences from other systems. There is no reason to suppose that anyone has yet come up with a perfect system of logic.
3. As mentioned earlier, logicians have not yet systematized all forms of logical thinking under axioms, rules, and laws of thought. So there may be legitimate inferences (from Scripture or other texts) that cannot be justified by current logical theory.
4. Sometimes arguments that appear to be logically valid turn out to be invalid on closer inspection. An example would be: All (human beings) have sinned (Rom. 3:23); Jesus is a human being (1 Tim. 2:5); therefore Jesus has sinned. The logic here appears valid. But a major rule of logic is that for such a syllogism to be valid the quantifier (“all” in this case) must include the objects to which the conclusion is applied. In this example, it is clear that Paul was not thinking of Jesus when he wrote that “all have sinned,” nor did he mean to deny the sinlessness of Christ, which he affirms in 2 Cor. 5:21 with other New Testament writers (John 8:46, Heb. 4:15, 7:26, 1 Pet. 2:22, 1 John 3:5). Here “all” does not have the universal force it needs to have, to make the syllogism valid.
Another rule of logic is that in a valid argument the terms must preserve the same meanings throughout the argument. One might argue: Everyone who believes in Christ has eternal life (John 3:16); some believers said that Jesus had a demon (John 8:31, 48); therefore some who believe Jesus has a demon have eternal life. The argument appears valid, but on closer inspection we note that it equivocates on the word “believe,” since the gospel writer himself uses “believe” in several senses. So determining logical validity is sometimes more complicated than it may appear on the surface.
5. Indeed, what the above examples prove is that the right use of logic presupposes the right use of other means of interpretation. In the first example, it is not enough to know the rules of logic. One must also understand the language well enough, and indeed to know enough about biblical Christology, to know the likely range of “all” in Rom. 3:23. Same in the second example: to see what is wrong with it, we must understand that the meaning of “believe” varies in Johannine use, and that it likely has a different meaning in John 3:16 from the meaning it has in 8:31. That is simply to say that right use of logic assumes a right understanding of language. Since I observed earlier that logic itself is a tool in the interpretation of language, we should draw the conclusion that knowledge of logic and language are mutually dependent.
6. Emerging from this discussion is the broader point that logic is in many ways dependent on other kinds of knowledge. Logic itself rarely supplies the premises of logical arguments. Those premises come from many sources, such as observation, reasoning, imagination, emotion, authority, and study. The use of logic, then, depends on empirical knowledge among other things. Philosophers have often claimed that logic is entirely a priori, not dependent on experience. Even if that is true of logic as an abstract system, it is not true of logic in actual practice. A logical argument will not yield a true conclusion unless its premises (usually derived from some source other than logic) are true.
7. Is the Bible logical, then? Granted that God is himself logical, and that Scripture is his infallible word, the (logical!) conclusion follows that Scripture is logical. That is, its teaching is logically consistent, and its arguments are valid. But given the problems noted above in the actual practice of logic, we should not be surprised to find in Scripture what Cornelius Van Til called “apparent contradictions.” These apparent contradictions are due not to logical errors in Scripture itself, but to our fallibility in interpreting and applying Scripture. The examples of #4 above may be reconceived as apparent contradictions: Christ is (Rom. 3:23) and is not (2 Cor. 5:21) a sinner; belief in Christ does (John 3:16) and does not (John 8:31-58) lead to eternal life. These “apparent contradictions” can be resolved by better hermeneutics and logic. But other apparent contradictions may not be resolvable except in the mind of God. The most difficult logical problems are the doctrine of the Trinity, the relation of divine sovereignty and human responsibility, the goodness of our first parents and the sin they committed, and the problem of evil. I see no reason why theologians should not attempt to resolve these as they have resolved the others. But there is no guarantee that we will be able to resolve these with our human systems of logic and our actual use of logic. Perhaps the resolution of some of these paradoxes awaits the next life, or perhaps only God’s perfect logic has the answers.
Clark, Gordon H. Logic. Jefferson, MD: Trinity Foundation, 1985; Copi, Irving M. Introduction to Logic. New York: Macmillan, 1972; Frame, John M., Cornelius Van Til: An Analysis of His Thought. Phillipsburg,NJ: P&R Publishers, 1995, 151-175; Doctrine of the Knowledge of God. Phillipsburg, NJ: P&R Publishers, 1987, 242-301; Quine, W. V., From a Logical Point of View. N. Y.: Harper and Row, 1961. Van Til, Cornelius. A Christian Theory of Knowledge. No place of publication listed: Presbyterian and Reformed Publishing Co., 1969, 37-40.