Five logical fallacies to avoid

Welcome to The Theology Whisperer, a series of short blog posts on theology and theological education.


In previous posts I defined logical fallacies, and suggested ways to avoid the use of fallacies in your own work. In this post I outline five common fallacies and give examples of each and a brief commentary. All of these are informal fallacies.


  1. Hasty generalisation


A general statement about something inferred from too few instances of that thing.


    • “I studied hard for my first two exams and failed. I’m not going to bother studying for my third, because I know I’m going to fail anyway.”
    • “I have two friends who drive Fords and they have nothing but trouble with them. Fords are rubbish cars.”
    • “I must wear my lucky socks. We never lose a game when I wear these socks.”
    • Simpsons logical fallacies: Hasty generalization (Colburn Classroom on YouTube)

In these examples, the sample size is too small to support a general conclusion. Many prejudices and superstitions are based on this fallacy. The word “prejudice” literally means “judgment made in advance of the facts.” One way to avoid this fallacy is to use qualifiers such as “sometimes,” “maybe,” “often,” or “it appears to be the case that…”

Hasty generalisations are common because sweeping statements attract attention, and there is no agreed upon measure for what constitutes “sufficient” evidence.

Generalisations do have their place, ideally using a large sample set with controlled variables and/or compelling particular examples supporting a claim. As Baggini and Fosl note, “The answers philosophers put forward to their questions commonly involve generalizations and universals … But it is because these answers are supposed to have universal application that individual cases become very important again, for an exceedingly powerful tool in philosophical thinking is the skill of deploying particular examples that undermine or at least qualify general claims” (81f).

See also Rottenberg & Winchell, 316; Withey, 125f.


  1. Appeal to doubtful authority


Appeal to the testimony of an “authority” in place of direct evidence. Such authority may be irrelevant (e.g. having no authority in the field in question), poor (e.g. biased or a novice), or false. Also known as argumentum ad verecundiam.


    • “My dad says that scientists planted dinosaur bones to discredit evolution. Therefore, evolution is false.”
    • “Four out of ten dentists agree that brushing your teeth makes your life meaningful.”
    • “More doctors smoke Camel than any other cigarettes.”
    • Simpsons logical fallacies: appeal to doubtful authority (Colburn Classroom on YouTube)

Appeal to authority is justified if the authority is an expert on the subject, but evidence should accompany such appeal. Note also that experts are not necessarily impartial.

You can challenge appeals to doubtful authority by demanding proof of the authority’s credentials to comment on the subject: Do they represent a consensus of experts in the field? Are they independent of vested interests?

See also Rottenberg & Winchell, 317; Withey, 43f.


  1. False analogy


Comparison of two things on the basis of superficial similarities while ignoring significant dissimilarities.


    • “Churches are no different from businesses. Therefore, they should be run as businesses.”
    • “Trying to educate couples for marriage is like trying to teach them to swim without allowing them to get in the water.”
    • We should never permit human cloning. It will create another Frankenstein’s monster. We don’t want such monsters.
    • Simpsons logical fallacies: a similar fallacy is the weak analogy (Colburn Classroom on YouTube)

This fallacy is often based on insufficient evidence. It makes a claim about some known or uncontested case, but we cannot readily assume that anything about the uncontested case holds true of the contested case. Some slippery slope arguments are extensions of this fallacy.

In creative writing, comparison may be made between two dissimilar items in order to invoke a literary effect (e.g. “it was raining wellington boots”), but in academic writing this is inappropriate.

To counter a false analogy, seek to show that the cases are in fact dissimilar.

See also Cottrell, 96; Rottenberg & Winchell, 318; Withey, 119-121.


  1. Ad hominem


Literally “against the man.” An attack on the character or motives of the person rather than the issue or argument, implying that, because the person is perceived as unacceptable in some way, his or her statements must also be judged unacceptable.


    • “We can dismiss Friedrich Nietzsche’s philosophy because he went mad in his later years.”
    • “She can’t be a church elder – she had her first child before she was married.”
    • “The CEO of that company is gay, so I won’t pay for their services.”
    • “Maybe I misused the petty cash, but so did Tony.”
    • Simpsons logical fallacies: ad hominem (Colburn Classroom on YouTube)

An ad hominem attack seeks to undermine the credibility of an opposing point of view, distracting from the issue and evidence. Such attacks are not fallacious if the character (e.g. dishonesty) or motives (e.g. vested interest in an outcome) of the person attacked are relevant to the argument.

For example, “If the politician is irresponsible or dishonest in the conduct of his or her personal life, we may be justified in thinking that the person will also behave irresponsibly and dishonestly in public office” (Rottenberg & Winchell, 319).

Withey discusses four types of ad hominem fallacy:

    • abusive: attacking a person’s argument by insulting the speaker.
    • circumstantial: undermining an argument’s credibility by appealing to some facts about its proponent, where these facts are inconsistent with the proponent’s advocacy of the argument, or where the facts undermine the proponent’s credibility in putting forward the argument.
    • guilt by association: attacking an argument by casting aspersions on people or organisations associated with either its proponents or the argument itself.
    • tu quoque (“you also”): an attempt to divert blame, undermining an argument against a behaviour or action by asserting that the proponent engages in the same behaviour or actions. It distracts from the argument by alleging hypocrisy in an opponent. It is not a fallacy to point out hypocrisy where it occurs – only where the allegation is used to neutralise criticism and distract from the issue.

See also Cottrell, 101-103; Rottenberg & Winchell, 319; Withey, 16-18.


  1. False dilemma


Also known as the “black-white fallacy,” or the “either-or fallacy,” this fallacy poses an either-or situation in which no other options are entertained, when the two options are neither exclusive nor exhaustive.


    • “If we elect a Labor government, the economy will suffer.”
    • “Australia – love it or leave it.”
    • Hagar cartoon in which Hagar’s wife offers him a plate of food, saying, “You have two choices for dinner – take it or leave it.”
    • Simpsons logical fallacies: false dilemma (Colburn Classroom on YouTube)

This fallacy reflects the simplification of a complex problem. It overlooks or ignores alternatives. The fallacy works because it presents properties as contradictory rather than contrary. As Withey notes, “Two properties are contrary when something cannot have both properties; they are contradictory when anything must have either one or the other” (p. 124). It is employed in political surveys to steer respondents toward a desired response.

Ethical arguments are especially prone to false dilemmas. To avoid this fallacy, think of alternatives outside the box (e.g. an action or event may occur for several reasons, not just one).

See also Baggini, 88f; Rottenberg & Winchell, 319f; Withey, 122-124; Wright, 380f.

I’ll take a look at some more fallacies in my next post in the series.


This post was written by Rod Benson. Leave a comment in the box below, or email 

References for all posts in this series on logical fallacies:

    • Ali Almossawi, An Illustrated Book of Bad Arguments (2nd edition; New York: Experiment, 2014).
    • Arp, Robert, Bad Arguments: 100 of the Most Important Fallacies in Western Philosophy (Hoboken, NJ: John Wiley & Sons, 2018).
    • Baggini, Julian & Fosl, Peter S., The Philosopher’s Toolkit: A Compendium of Philosophical Concepts and Methods (Oxford: Blackwell Publishing, 2003), especially pp. 66-132.
    • Carson, D. A., Exegetical Fallacies (2nd edition; Grand Rapids: Baker Academic, 1996).
    • Cottrell, Stella, Critical Thinking Skills: Effective Analysis, Argument and Reflection (3rd edition; London: Red Globe Press, 2017).
    • Mather, Peter, The Art of Critical Reading: Brushing Up Your Reading, Thinking, and Study Skills (4th edition; New York: McGraw-Hill Education, 2016).
    • Rottenberg, Annette & Winchell, Donna Haisty, The Structure of Argument (9th edition; Boston: Bedford St Martin’s, 2018).
    • Trueman, Carl R., Histories and Fallacies: Problems Faced in the Writing of History (Wheaton: Crossway, 2010), especially pp. 141-168.
    • Withey, Michael, Mastering Logical Fallacies: The Definitive Guide to Flawless Rhetoric and Bulletproof Logic (Berkeley, CA: Zephros Press, 2016).
    • Wright, Larry, Critical Thinking: An Introduction to Analytical Reading and Reasoning (2nd edition; Oxford: Oxford University Press, 2013), especially pp. 376-391.

Image source: ad hominem fallacy

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