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Why Logical Fallacies Work

The Death of Socrates, by Jacques-Louis David (1787).
The Death of Socrates, by Jacques-Louis David (1787). Plato believed that bad arguments had condemned his teacher to death, inspiring Aristotle’s search for the principles of sound reasoning.

History is full of brilliant minds who believed false things and defended absurd ideas. Isaac Newton spent decades trying to create the philosopher’s stone. Thomas Edison championed radioactive products as remedies for various ailments. Steve Jobs skipped bathing in the conviction that his vegan diet could cleanse his body of mucus and toxins.

The problem is not that intelligent people cannot think.

It is that they are human.

We all have hopes, fears, loyalties, ambitions, prejudices, and desires. We are naturally drawn to arguments that flatter our opinions, excuse our behaviour, or confirm our suspicions.

More than two thousand years ago, the ancient Greeks began studying arguments that were unsound and yet persuasive, calling them fallacies.

Learning to recognise them remains one of philosophy’s most practical lessons. But more interesting than what they are is how they work.

Why Bad Arguments Persuade Us

Most fallacies succeed not because they overwhelm our intelligence, but because they appeal to our human nature and frailties.

We are more receptive to arguments that confirm what we already believe than to those that ask us to change our minds. We welcome arguments that flatter our side, condemn our opponents, simplify a complicated world, or promise certainty where none exists.

Reason is less often an impartial judge than a disingenuous lawyer, excelling at defending conclusions that we reached for wholly other reasons.

And, sadly, the brighter the mind, the more elaborate—and persuasive—its rationalisations.

From Rhetoric to Logic

The study of fallacies emerged in ancient Greece as a branch of rhetoric, the art and science of persuasive speaking.

Following the reforms of Cleisthenes in 508 BCE, Athens became a radically participatory democracy. Citizens served as jurors, debated laws, and competed for influence not with swords but with words.

Sophists such as Gorgias, Protagoras, and Hippias enriched themselves by teaching this new art of persuasion. Gorgias was not merely a teacher of rhetoric, but a performer, master of verbal display, and intellectual celebrity. According to tradition, when he appeared in the theatre at Athens, he would invite the audience: “Come, propose me a theme.” He took pride in his ability to speak on any subject and defend even the most improbable of positions.

For Plato, this represented a profound problem. It had been by bad arguments that his teacher, Socrates, had been put to death. If persuasive speech could triumph over truth, what hope could there be for philosophy?

Plato’s pupil Aristotle sought to address these concerns by laying the foundations of logic.

If rhetoric explains how people are persuaded, logic asks when they ought to be.

Formal and Informal Fallacies

Logic distinguishes two broad kinds of fallacy: formal and informal.

A fallacy is a defect in an argument, whether accidental or deliberate.

Formal fallacies arise from the structure of an argument.

If I have the flu, then I have a fever.
I have a fever.
Therefore, I have the flu.

The conclusion, of course, does not follow, since I may have any number of other pyrogenic (fever-inducing) illnesses.

This formal fallacy is known as affirming the consequent.

Far more common are informal fallacies, whose weakness lies not in their logical form but in their content.

These are the fallacies that fill newspaper columns, political debates, boardrooms, dinner tables, and social media.

We Prefer People to Arguments

The easiest way to answer an argument is often not to answer it at all.

Instead, attack the person making it.

This is the ad hominem fallacy.

Closely related are the genetic fallacy, which judges an argument by its source, and the appeal to hypocrisy (tu quoque), which dismisses an argument because its author fails to live by it.

None addresses the argument itself.

They succeed because judging people is easier than judging ideas.

A striking example of the genetic fallacy came during the 2016 Brexit referendum. On 3 June 2016, the then Lord Chancellor, Michael Gove, declared: ‘The people in this country have had enough of experts…’

We Prefer Easy Victories

Some arguments are difficult to refute.

It is then much easier to invent a weaker one.

A straw man caricatures an opponent’s position before knocking it down.

Closely related is the red herring, which changes the subject altogether.

Neither brings us closer to the truth, but both bring us closer to victory.

Some regard straw man as a form of red herring, since both serve to deflect. ‘Red herring’ takes its name from the custom of using stinky smoked herring to throw dogs off a trail. Think of it as a form of pre-Internet trolling.

For example:

—Critical appraisal of the new Bordeaux vintage would be more objective and meaningful if the wines could be tasted blind.

—Just Bordeaux?

We Prefer Agreement

Human beings are social animals.

This makes us especially vulnerable to social arguments.

An appeal to popularity asks us to believe something because many other people believe it.

An argument to moderation assures us that the middle position must be right.

A false dilemma presents only two options when reality usually offers many more.

These fallacies appeal to our desire for belonging, certainty, and simplicity.

False dilemma is often a veiled attempt to force a Hobson’s choice of ‘take it or leave it’. For example, Theresa May insisted: ‘It’s my deal or no deal.’ At times, she expanded this into a false trilemma: ‘It’s my deal, no deal, or no Brexit at all.’

We Prefer Simple Stories

The human mind delights in finding patterns—so much so that it finds them where none exist.

Cum hoc ergo propter hoc (‘with this, therefore because of this’) mistakes correlation for causation.

The gambler’s fallacy imagines that independent events, like a throw of dice, somehow remember what came before.

Both satisfy our hunger for neat explanations in a messy world.

Cum hoc ergo propter hoc is also known as the Chanticleer fallacy after the fictional rooster who believed that his crowing made the sun rise. I prefer to think of it as the scientist’s fallacy.

We Prefer Being Right

Perhaps the most bone-headed fallacy of all is begging the question.

Instead of proving a conclusion, it quietly assumes it.

For example, the argument that opposes same-sex marriage on the grounds that marriage is the union between a man and a woman is no more substantial than ‘I’m right because I’m right.’

Circular arguments persuade because they begin where we already stand.

The Discipline of Thinking Clearly

This article may have seemed to be about reasoning.

It has really been about self-deception.

Logical fallacies endure because they satisfy our desires more readily than they satisfy the demands of reason.

We rarely believe bad arguments because we cannot think.

More often, we believe them because they tell us what we wanted to hear.

Learning to recognise fallacies in others is useful.

Learning to recognise them in ourselves is the beginning of self-knowledge.

Continue Exploring

If you enjoyed this introduction to logical fallacies, you’ll find many more practical lessons on reasoning and rhetoric in How to Think Like Plato and Speak Like Cicero.

To explore the forces that so often lead us astray, see Hide and Seek: The Psychology of Self-Deception.

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The five enemies of rational thought.

Following his defeat at the Battle of Actium in 31 BCE, Marc Antony heard a rumour that Cleopatra had committed suicide and, in consequence, stabbed himself in the abdomen—only to discover that Cleopatra herself had been responsible for spreading the rumour. He later died in her arms.

“Fake news” is nothing new, but in our Internet age it has spread like a contagious disease, swinging elections, fomenting social unrest, undermining institutions, and diverting political capital away from health, education, the environment, and all-round good government.

So how best to guard against it?

As a medical specialist, I’ve spent over 20 years in formal education. With the possible exception of my two-year masters in philosophy, the emphasis of my education has always been firmly and squarely on fact accumulation.

Today, I have little use for most of these facts, and though I am only middle-aged, many are already out of date, or highly questionable.

But what I do rely on—every day, all the time—is my faculty for critical thinking. As BF Skinner once put it, “Education is what survives when what has been learnt has been forgotten.”

But can critical thinking even be taught?

In Plato’s Meno, Socrates says that people with wisdom and virtue are very poor at imparting those qualities: Themistocles, the Athenian politician and general, was able to teach his son Cleophantus skills such as standing upright on horseback and shooting javelins, but no one ever credited Cleophantus with anything like his father’s wisdom; and the same could also be said of Lysimachus and his son Aristides, and Thucydides and his sons Melesias and Stephanus.

In Plato’s Protagoras, Socrates says that Pericles, who led Athens at the peak of its golden age, gave his sons excellent instruction in everything that could be learnt from teachers, but when it came to wisdom, he simply left them to “wander at their own free will in a sort of hope that they would light upon virtue of their own accord”.

It may be that wisdom and virtue cannot be taught, but thinking skills certainly can—or, at least, the beginning of them.

So rather than leaving thinking skills to chance, why not make more time for them in our schools and universities, and be more rigorous and systematic about them?

I’ll make a start by introducing you to what I have called “the five enemies of rational thought”:

1. Formal fallacy. A fallacy is some kind of defect in an argument. A formal fallacy is an invalid type of argument. It is a deductive argument with an invalid form, for example:

Some A are B. 
Some B are C. 
Therefore, some A are C.

If you cannot yet see that this argument is invalid, substitute A, B, and C with “insects”, “herbivores”, and “mammals”.

Insects, clearly, are not mammals.

A formal fallacy is built into the structure of an argument and is invalid irrespective of the content of the argument.

2. Informal fallacy. An informal fallacy, in contrast, is one that can only be identified through an analysis of the content of the argument.

Informal fallacies often turn on the misuse of language, for example, using a key term or phrase in an ambiguous way, with one meaning in one part of the argument and another meaning in another part—called “fallacy of equivocation”.

Informal fallacies can also distract from the weakness of an argument, or appeal to the emotions instead of reason.

Here are a few more examples of informal fallacies.

  • Damning the alternatives. Arguing in favour of something by damning its alternatives. (Tim’s useless and Bob’s a drunk. So, I’ll marry Jimmy. Jimmy’s the right man for me.)
  • Gambler’s fallacy. Assuming that the outcome of one or more independent events can impact the outcome of a subsequent independent event. (June is pregnant with her fourth child. Her first three children are all boys, so this time it’s bound to be a girl.)
  • Appeal to popularity. Concluding the truth of a proposition on the basis that most or many people believe it to be true. (Of course he’s guilty: even his mother has turned her back on him.)
  • Argument from ignorance. Upholding the truth of a proposition based on a lack of evidence against it, or the falsity of a proposition based on a lack of evidence for it. (Scientists haven’t found any evidence of current or past life on Mars. So, we can be certain that there has never been any life on Mars.)
  • Argument to moderation. Arguing that the moderate view or middle position must be the right or best one. (Half the country favours leaving the European Union, the other half favours remaining. Let’s compromise by leaving the European Union but remaining in the Customs Union.)

You can find many more examples in Hypersanity: Thinking Beyond Thinking.

3. Cognitive bias. Cognitive bias is sloppy, if not necessarily faulty, reasoning: a mental shortcut or heuristic intended to spare us time, effort, or discomfort—often while reinforcing our self-image or worldview—but at the cost of accuracy or reliability.

For example, in explaining the behaviour of other people, our tendency is to overestimate the role of character traits over situational factors—a bias, called correspondence bias, that goes into reverse when it comes to explaining our own behaviour. Thus, if Charlotte fails to mow the lawn, I indict her with forgetfulness, laziness, or spite; but if I fail to mow the lawn, I absolve myself on the grounds of busyness, tiredness, or inclement weather.

Another important cognitive bias is my-side, or confirmation, bias, which is the propensity to search for or recall only those stories, facts, and arguments that are in keeping with our pre-existing beliefs while filtering out those that conflict with them—which, especially on social media, can lead us to inhabit a so-called echo chamber.

4. Cognitive distortion. Cognitive distortion is a concept from cognitive-behavioural therapy (CBT), developed by psychiatrist Aaron Beck in the 1960s and used in the treatment of depression and other mental disorders.

Cognitive distortion involves interpreting events and situations so that they conform to and reinforce our outlook or frame of mind, typically on the basis of very scant or partial evidence, or even no evidence at all.

Common cognitive distortions in depression include selective abstraction and catastrophic thinking.

Selective abstraction is to focus on a single and often insignificant negative event or condition to the exclusion of other, more positive ones, for example, “My partner hates me. He gave me an annoyed look three days ago.”

Catastrophic thinking is to exaggerate and dramatize the likely consequences of an event or situation, for example, “The pain in my knee is getting worse. When I’m reduced to a wheelchair, I won’t be able to go to work and pay the bills. So, I’ll end up losing my house and dying in the street.”

A cognitive distortion can open up a vicious circle, with the cognitive distortion feeding the depression, and the depression the cognitive distortion.

Cognitive distortion as broadly understood is not limited to depression and other mental disorders, but is also a feature of, among others, poor self-esteem, jealousy, and marital conflict.

5. Self-deception. Of the five enemies of rational thought, the most important by far is self-deception, because it tends to underlie all the others.

If we do not think clearly, if we cannot see the wood for the trees, this is not usually because we lack intelligence or education or experience, but because we feel exposed and vulnerable—and rather than come to terms with a painful truth, prefer, almost reflexively, to deceive and defend ourselves.

As I argue in Hide and Seek: The Psychology of Self-Deception, all self-deception can be understood in terms of ego defence. In psychoanalytic theory, an ego defence is one of several unconscious processes that we deploy to diffuse the fear and anxiety that arise when who or what we truly are (our unconscious “id”) comes into conflict with who we think we are or who we think we should be (our conscious “superego”).

To put some flesh onto this, let’s take a look at two important ego defences: projection and idealization.

Projection is the attribution of one’s unacceptable thoughts and feelings to other people. This necessarily involves repression (another ego defence) as a first step, since unacceptable thoughts and feelings need to be repudiated before they can be detached. Classic examples of projection include the envious person who believes that everyone envies her, the covetous person who lives in constant fear of being dispossessed, and the person with fantasies of infidelity who suspects that they are being cheated upon by their partner.

Idealization involves overestimating the positive attributes of a person, object, or idea while underestimating its negative attributes. At a deeper level, it involves the projection of our needs and desires onto that person, object, or idea. A paradigm of idealization is infatuation, or romantic love, when love is confused with the need to love, and the idealized person’s negative attributes are glossed over or even construed as positive. Although this can make for a rude awakening, there are few better ways of relieving our existential anxiety than by manufacturing something that is ‘perfect’ for us, be it a piece of equipment, a place, country, person, or god.

In all cases, the raw material of thought is facts. If the facts are missing, or worse, misleading, then thought cannot even get started.