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Michael Horton provides some examples of informal logical fallacies, which should be avoided when writing a theological paper in his classes (and, of course, in all of life!). I’ve reprinted below the ones that he lists (along with some images, which have some relevance to the fallacy in one way or another).

Ad Hominem

First and foremost we need to avoid the ubiquitous ad hominem (“to/concerning the person”) variety—otherwise known as “personal attacks.”

Poor papers often focus on the person: both the critic and the one being criticized. This is easier, of course, because one only has to express one’s own opinions and reflections. A good paper will tell us more about the issues in the debate than about the debaters. (This of course does not rule out relevant biographical information on figures we’re engaging that is deemed essential to the argument.)

Red Herring

Closely related are red-herring arguments: poisoning the well, where you discredit a position at the outset (a pre-emptive strike), or creating a straw man (caricature) that can be easily demolished.

“Barth was a liberal,” “Roman Catholics do not believe that salvation is by grace,” “Luther said terrible things about Jews and Calvin approved the burning of Servetus—so how could you possibly take seriously anything they say?”

It’s an easy way of dismissing views that may be true even though those who taught them may have said or done other things that are reprehensible.

Genetic Fallacy

Closely related is the genetic fallacy, which requires merely that one trace an argument or position back to its source in order to discount it.

Simply to trace a view to its origin—as Roman Catholic, Arminian, Lutheran, Reformed, Anabaptist/Baptist, etc.—is not to offer an argument for or against it. For example, we all believe in the Trinity; it’s not wrong because it’s also held by Roman Catholics. “Barth studied under Harnack and Herrmann, so we should already consider his doctrine of revelation suspect.” This assertion does not take into account the fact that Barth was reacting sharply against his liberal mentors and displays no effort to actually read, understand, and engage the primary or secondary sources.

Slippery Slope

Closely related to these fallacies is the all too familiar slippery slope argument. “Barth’s doctrine of revelation leads to atheism” or “Arminianism leads to Pelagianism” or “Calvinism leads to fatalism” would be examples. Even if one’s conclusion is correct, the argument has to be made, not merely asserted. The fact is, we often miss crucial moves that people make that are perfectly consistent with their thinking and do not lead to the extreme conclusions we attribute to them—not to mention the inconsistencies that all of us indulge. Honesty requires that you engage the positions that people actually hold, not conclusions you think they should hold if they are consistent.

If you’re going to make a logical argument that certain premises lead to a certain conclusion, then you need to make the case and must also be careful to clarify whether the interlocutor either did make that move or did not but (logically) should have.

Sweeping Generalization

Another closely related fallacy here is sweeping generalization. Until recently, it was common for historians to try to explain an entire system by identifying a “central dogma.” For example, Lutherans deduce everything from the central dogma of justification; Calvinists, from predestination and the sovereignty of God. Serious scholars who have actually studied these sources point out that these sweeping generalizations don’t have any foundation. However, sweeping generalizations are so common precisely because they make our job easier. We can embrace or dismiss positions easily without actually having to examine them closely. Usually, this means that a paper will be more “heat” than “light”: substituting emotional assertion for well-researched and logical argumentation.

“Karl Barth’s doctrine of revelation is anti-scriptural and anti-Christian” is another sweeping generalization. If I were to ask you in person why you think Barth’s view of revelation is “anti-scriptural anti-Christian,” you might answer, “Well, I think that he draws too sharp a contrast between the Word of God and Scripture—and that this undermines a credible doctrine of revelation.” “Good,” I reply, “now why do you think he makes that move?” “I think it’s because he identifies the ‘Word of God’ with God’s essence and therefore regards any direct identification with a creaturely medium (like the Bible) as a form of idolatry. It’s part of his ‘veiling-unveiling’ dialectic.” OK, now we’re closer to a real thesis—something like, “Because Barth interprets revelation as nothing less than God’s essence (actualistically conceived), he draws a sharp contrast between Scripture and revelation.” A good argument for something like that will allow the reader to draw conclusions instead of strong-arming the reader with the force of your own personality.

Begging the Question

Also avoid the fallacy of begging the question. For example, question-begging is evident in the thesis statement: “Baptists exclude from the covenant those whom Christ has welcomed.” After all, you’re assuming your conclusion without defending it. Baptists don’t believe that children of believers are included in the covenant of grace. That’s the very reason why they do not baptize them. You need an argument.

You can read the whole thing here, where he explains the importance of this for Christian piety and virtue.

For more on logical fallacies, you could consult a book like Peter Kreeft’s Socratic Logic or Norman Geisler and Ronald Brooks’s Come, Let Us Reason: An Introduction to Logical Thinking. Or see this nice free PDF summary chart, “Thou Shalt Not Commit Logical Fallacies.”

For more on essay writing in seminary, see this good overview by R. Scott Clark as well as this insight but more general piece by John Frame. Those in the UK could order the little book by Michael Jensen, How to Write a Theological Essay.

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16 thoughts on “Avoiding Logical Fallacies in Theology”

  1. Lindsay says:

    This is wonderful, thank you for reposting this (and for breaking the points into sections)

  2. Regarding the slippery slope argument, consider this: “Egalitarianism leads to a hermeneutic where the Gospel itself is lost.” This is my paraphrase of something John Piper said recently in a TGC video. Could this be an example of a slippery slope fallacy?

    This is a hopefully-perceived-as-respectful question from a Piper loving complementarian.

    1. Lindsay says:

      Did he provide reasons or examples? I suppose we’re all guilty of assuming our audience understands and/or agrees with assertions that make complete sense in our own mind.

  3. Jeff Kerr says:

    Even smart (and godly) men can make bad arguments sometimes.

  4. David P says:

    Great stuff. Following Horton’s advice would increase both the clarity and the charity of theological discussion.

    Just one thing made me wonder. Is it true of all Baptists that they “don’t believe that children of believers are included in the covenant of grace”? I have a feeling that many baptistic Christians would see the children of believers as in some sense in receipt of covenant blessings, whether or not it is consistent for them to do so. It might depend how technically one is using these words.

  5. I have often felt that a course in logic and logical fallacies should be a required course in school or at least in seminary. Thank you for re-posting this information.

    1. Just today I volunteered to be on the pastoral advisory committee for my old seminary. A course (or a least a couple of seminars) in logic is going to be one of my recommendations.

    2. John says:

      Yes please! Logic and argumentation should be absolutely required.

  6. Allen says:

    Thanks kindly for the post Justin! For some reason, I can’t seem to get my head around “Begging the Question.” Is it considered “Begging the Question” because the writer simply states the thesis without defending the position? Or is there something inherently circular in the thesis statement that makes the actual thesis statement fallacious. Thanks!

    1. John says:

      Allen, petitio principii is an assertion that needs proof presented without proof. So, sometimes it can look like a bare assertion. More often, though, this fallacy occurs when someone pretends to give proof, but hasn’t, really. The most obvious example is hysteron proteron, where synonyms are used to mask lack of argument, e.g. “Cinnamon causes sexual arousal because it is a natural aphrodisiac.” In the previous sentence, “aphrodisiac” is a synonym for “causes sexual arousal”. So, this isn’t an argument at all, but a tautology! More complex question begging includes several steps, but generally takes the form of pushing the dubious nature of the assertion back onto certain presuppositions. By moving the doubt from the assertion to its premises, the weakness of an assertion can be masked.

      1. Allen says:

        Thanks for your thorough explanation. Quite helpful!

  7. Marisme says:

    I am glad to see the ‘slippery slope’ argument included in the above list. It is used too often to fabricate FUD (fear, uncertainty, doubt) towards an opposing view or to discredit it entirely. We hear it used over and over in discussions regarding such topics as cultural context of Scripture, biblical inerrancy, complementarianism/egalitarianism, homosexuality, etc…

    God is a lot bigger than our ability to achieve perfect knowledge and needs no defense from us to remain The Omnipotent God. He is quite capable of navigating double-black diamonds.

  8. brett schlee says:

    Hey, Justin,

    How do you deal with pictures and copyright issues? I’m starting a blog and found out (I think) that it is illegal to post pictures (unless they’re public domain) without the copyright holder’s express permission. So for example, did you get the permission of the studio that made “A Few Good Men” to post the Jack Nicholson pic in this article?

  9. Betsy says:

    With respect, I think there may be a few errors in this post worth commenting on. One in particular–I believe that neither “poisoning the well” nor the “straw man are actually examples of a red herring, which implies introducing information that is confusing or distracting from the main issue. (see, for example:

    Also, what about the “appeal to authority” fallacy–of appealing to unnamed experts to support a point? An example of this: “Serious scholars who have actually studied these sources point out that these sweeping generalizations don’t have any foundation.”

    I do think this was an interesting post and otherwise helpful, thank you.

  10. Gary says:

    Justin, this entire post is nothing but a non-sequiter. :)

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Justin Taylor, PhD

Justin Taylor is executive vice president of book publishing and book publisher for Crossway and blogs at Between Two Worlds. You can follow him on Twitter.

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