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Logic (from the Greek word logos, "reason") is the "science that deals with the principles and criteria of validity of inference and demonstration, the science of the formal principles of reasoning" (Merriam-Webster). While theology, as the study of God, transcends mere logic, it is reasonable to expect that Scripture adheres to common principles of reasoning. Properly used, logic derives true propositions from other true propositions. Even though Scripture may not explicitly state a given truth, we may make true statements that have Scripture's authority behind them if they are properly derived from what Scripture does say following principles of logical reasoning.

A basic understanding of the rules of logic is crucial to sound hermeneutics. Logical fallacies, both formal and informal, are found in every field of study, and biblical exegesis is no exception. In what follows, I will provide examples of some of the most common logical fallacies encountered in biblical studies. They are: (1) false disjunctions, (2) appeals to selective evidence, (3) unwarranted associative jumps, (4) improperly handled syllogisms, (5) false statements, and (6) non sequiturs.

False disjunctions are made when an argument is presented in an either or fashion: either A or B is true, but not both. However, there are times when the answer is "both/and" rather than "either/or." Take the relationship between Galatians 3:28 and 1 Timothy 2:12, for example. It is at times claimed that Paul's assertion in Galatians 3 that in Christ there is "no male and female" eradicates all gender-related distinctions with regard to church ministry, so that the prohibition of women teaching or exercising authority over men in the church in 1 Timothy 2 must be explained as a culturally relative injunction. Both— undifferentiated male-female equality in Christ and limiting authoritative local church offices to men—cannot be true, it is said (or at least implied), so the latter principle must be relativized in such a way that it fits with the former. However, this kind of disjunctive thinking is fallacious. Since 1 Timothy 2:12 is grounded in creation's design and, conversely, the scenario at the fall (vv. 13–14), the passage cannot easily be set aside as culturally bound. More promising is the explanation that Galatians 3:28, in affirming the irrelevance of male-female distinctions with regard to salvation in Christ, is not seeking to address male-female roles in the church at all, so that the passages are pertaining to different (albeit related) topics. Both affirmations are true: men and women are indiscriminately saved by grace through faith in Christ, and the office of elder/overseer is reserved in Scripture for men in keeping with God's creation design.

Appeals to selective evidence are numerous. By definition, we engage in this logical fallacy anytime we only refer to authorities or passages that agree with us on a given issue while failing to account for countervailing evidence or authorities. A specific example comes from the "name it and claim it" theology. In circles that embrace this sort of thinking, it is common to cite Scripture passages that promise answers to prayer for "whatever you ask." For example, in John 14:13–14 Jesus says: "Whatever you ask in my name, this I will do, that the Father may be glorified in the Son. If you ask me anything in my name, I will do it." At other times, Scripture stresses the need for faith on the part of the one who prays (Heb. 11:6; James 1:6). However, people can sustain the name-it-and-claim- it approach only by selective use of evidence while ignoring other passages that put certain constraints on the kinds of prayers God will answer: prayers of disciples who take up their cross and follow Jesus, prayers asking for resources to carry out God's mission in the world, and so on. Such proponents also tend to ignore the mystery of suffering (see, for example, Jesus' comments in Luke 13:1–6), fail to explain why God answers certain prayers but not others (such as for the salvation of loved ones), and neglect to point out that there is no scriptural guarantee that God will answer all prayers for healing.

Unwarranted associative jumps, likewise, are treacherous and lurk at every turn. D.A. Carson, in his excellent book Exegetical Fallacies, cites the classic example of Paul's statement in Philippians 4:13, "I can do all things through him who strengthens me." All things? As Carson rightly points out, Paul's statement cannot be legitimately extended to such things as jumping over the moon, integrating complex mathematical equations in one's head, or turning sand into gold.

Certain constraints are brought to bear by the context of Paul's statement in his letter to the Philippians, most importantly the importance of contentment and of being able to deal with both poverty and wealth. Another common example of an associative jump is taking 2 Chronicles 7:14 ("If my people who are called by my name humble themselves . . . ") as directly applying to modern-day democracies when the original point of reference was to Israel as a theocracy.

Improperly handled syllogisms are very common as well. An example of a two-step argument for women serving authoritatively in the church based on the application of the term co-worker (Greek synergos) to both Timothy (Rom. 16:21) and women such as Euodia and Syntyche (Phil. 4:2–3) might look as follows:

Syllogism No. 1:

  1. Timothy is a co-worker of Paul.
  2. Timothy functioned authoritatively in the church.
  3. Therefore, all co-workers of Paul functioned authoritatively in the church.

Syllogism No. 2:

  1. Euodia and Syntyche are co-workers of Paul.
  2. All co-workers of Paul functioned authoritatively in the church (the conclusion of the first syllogism).
  3. Therefore, Euodia and Syntyche functioned authoritatively in the church.

However, there are several problems with this kind of reasoning. Most importantly, the first syllogism is invalid: the conclusion does not properly follow from the premises. That is, if one were to say (1) some A is B and (2) all B is C, then one cannot from these premises categorically conclude that (3) all A is C.

At best, one could seek to work inductively and contend that there is a strong likelihood that all co-workers of Paul functioned (or could function) authoritatively in the church. However, this would be a difficult case to prove, because contextual study of the relevant passages suggests that co-worker in the New Testament is a more flexible term that may indicate various forms of partnership, whether joint ministry, financial support, or other ways of collaboration. In any case, our point here is that arguments based on syllogisms, while common and often having surface appeal, may turn out at closer scrutiny to be fallacious and unsustainable.

False statements are also quite common, though perhaps this category would better be labeled "the use of faulty premises." This fallacy may also be related to the just-mentioned faulty use of syllogisms. Remember, even if a syllogism is formally valid, as we have seen, the conclusion may still be false if one or both of the premises are faulty. An example of this is the common manner of citing Proverbs 29:18: "Where there is no vision, the people perish," with vision being used to indicate a leader's or group's forward-looking plans, desires, and expectations instead of the prophetic revelation that seems to be in view here. This is wisely brought out by the ESV translation of the verse: "Where there is no prophetic vision the people cast off restraint" (emphasis added).

While I could continue, I'll close with one of my favorite categories, that of non sequiturs (Latin for "does not [logically] follow"). Many examples could be given, but perhaps most common under this rubric are illegitimate arguments from silence. For example, consider the not-uncommon assertion that the reason why Mark and John don't mention the virgin birth is that they either didn't know about it or, if they did, didn't believe in it. This clearly doesn't follow logically and is both a non sequitur and an illegitimate argument from silence. What about other reasons, such as Mark's desire for concision or John's reference to Jesus' eternal preexistence as the Son of God?

Even more importantly, I'd love to have a nickel for every time I've heard the argument that because Jesus never explicitly addressed the subject of homosexuality, we can safely surmise that He condoned such a practice. This assertion, of course, overlooks the fact that Jesus unequivocally stated, "Have you not read that he who created them [the man and the woman] from the beginning made them male and female, and said, 'Therefore a man shall leave his father and his mother and hold fast to his wife, and the two shall become one flesh?'" (Matt. 19:4–5). It is hard to infer from this strong affirmation of heterosexual marriage that Jesus condoned same-sex marriage.

These examples highlight the importance of engaging in proper logical reasoning when interpreting Scripture. I don't have space to address numerous other fallacies here, such as those related to emotive appeals, cavalier dismissals, improper analogies, simplistic appeals to authority, fallacies based on equivocal argumentation, and the improper use of obviously and similar expressions. Suffice it to say that every worker who truly desires God's approval in his handling of Scripture (2 Tim. 2:15) will do well to apply himself earnestly to sound principles of logic and proper reasoning.