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How Logical Fallacies Exploit Human Nature

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.

By Dr Neel Burton — Psychiatrist, philosopher, and wine writer; Fellow of Green Templeton College, University of Oxford; author of over twenty books.

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 moderationassures 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.

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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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19th century cartoon of Cicero denouncing Catiline

When and how to use them, and how to defend against them.

In rhetoric, an ad hominem (“to the man”) is an attack, not on the argument itself, but on the person making it. It is, in simpler words, an attempt to shoot the messenger.

When Winston Churchill called Mahatma Gandhi “a seditious Middle Temple lawyer now posing as a fakir,” he was attempting to undermine Gandhi’s character, or ethos.

Ad hominem, which is essentially an attack on a speaker’s ethos, is older than the books. It was not beneath Churchill, or even the Roman orator Cicero, who used it often, and went so far as to call Piso, Julius Caesar’s father-in-law, a “most foul and inhuman monster” (inhumanissimum ac foedissimum monstrum).

The first and most famous line of the most famous speech in all of Latin literature, Cicero’s First Catilinarian, is no more than an extended ad hominem:

When, O Catiline, do you mean to cease abusing our patience? How long is that madness of yours still to mock us? When is there to be an end to that unbridled audacity of yours, swaggering about as it does now?

When and how to use ad hominem

In academic circles, the ad hominem is regarded as a logical fallacy and frowned upon. It is uncivil, it stifles debate, and it is a tacit admission that you are losing the argument. It is forbidden in formal debates, and there has been a petition to ban it from the U.K.’s House of Commons.

But in rhetoric, anything goes, and an ad hominem can be legitimate if it serves to undermine the ethos, or pro hominem claims, of your opponents.

Even so, when attacking an opponent, it is better to put one’s words into the mouth of some third person, or to use paralipsis (mentioning something by saying that you will not mention it), as Cicero did in his speech Pro Caelio:

Clodia, I am not thinking now of the wrongs you have done me. I am putting to one side the memory of my humiliation. I pass over your cruel treatment of my family when I was away. Consider that nothing I have said has been said against you.

While debating Ron DeSantis, former Florida gubernatorial candidate Andrew Gillum succeeded in doing both at the same time, to great effect:

I’m not calling Mr. DeSantis a racist; I’m simply saying the racists believe he is a racist.

Such is the power of rhetoric that, had it not been for this single sentence, I may never have heard of Andrew Gillum. Often, when all is said and done, all that remains of a life is one or two sententiae, if even that.

How to defend against ad hominem

If you find yourself on the receiving end of an ad hominem, you can respond in one of four ways:

  1. Ignore it.
  2. Call it out as an ad hominem, e.g. “Instead of attacking me, could you please return to the argument, which you seem afraid of losing.”
  3. Own it.
  4. Bite back with an ad hominem of your own.

Which strategy to use depends on the context and the available material (so always do your research). But in the absence of a killer riposte, it is best and easiest to ignore the insult while looking slightly dismayed.

Finally, if returning an ad hominem, consider accompanying or accenting it with some gesture—the rhetorical device known as mycterismus. If the audience laughs, which it probably will, your opponent will not recover from it.

Neel Burton is author of the newly published How to Think Like Plato and Speak Like Cicero.

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Why speakers shouldn’t always pander to their audience.

In the Rhetoric (4th century BCE), Aristotle identified the three modes of persuasion, or persuasive appeals, that are in: the character of the speaker (ethos), the emotions of the audience (pathos), and the argument itself (logos).

Ethos, pathos, and logos are referred to as artistic means of persuasion, and contrasted to non-artistic means, that is, to hard evidence, such as laws, witnesses, and contracts.

Ethos and decorum

In a speaker, ethos is also a matter of agreeability and meeting the expectations of the audience in terms of appearance, diction, and comportment. The Romans referred to this aspect of ethos as decorum.

Anything that grates with the audience, or sets you apart from it, is a violation of decorum. What this might be varies from audience to audience. For example, an audience of academics would expect some jargon, which, however, would jar with a general audience. Boastfulness and vulgarity can be a violation of decorum, as can be, unfortunately, complexity and subtlety.

In the Rhetoric, Aristotle remarks that it is their simplicity that makes the uneducated more effective than the educated before a general audience:

It is this simplicity that makes the uneducated more effective than the educated when addressing popular audiences—makes them, as the poets tell us, “charm the crowd’s ears more finely.” Educated men lay down broad general principles; uneducated men argue from common knowledge and draw obvious conclusions.

When to break decorum

The rhetorician Quintilian (d. c. 100 CE), author of the Institutes of Oratory, points out that what might de decorous in the eyes of an audience might be repugnant under the aspect of eternity, that is, in the eyes of God.

In example, Quintilian cites the trial of Socrates: how would this paragon of virtue be remembered today if, instead of standing up to them and rebuking them, he had sought to meet the expectations of the jurors by shedding tears, resorting to prayers and supplications, and bringing forth his young children?

Today in America, many politicians are grappling with just this problem in addressing their base. It is much easier to be decorous before an audience that is itself decorous.

How to break decorum

So how to go about telling an audience something that it doesn’t want to hear?

One strategy is to appear to have reached your conclusion reluctantly, driven only by the overwhelming force of the argument. You might even use a technique known as the dubitatio, which involves expressing doubt or uncertainty about what to say.

Another approach is to make your conclusion seem like a concession in the face of an even greater evil, such as inflation or recession.

And the third thing is to make your stance seem in line with the orthodoxy, as when Elon Musk (himself a South African) defended the skilled immigrant visa as “American”.

These techniques work for politicians and public figures, and they will also work for you.

Neel Burton is author of How to Think Like Plato and Speak Like Cicero

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If you love words, read on.

Gorgias mesmerising his audience.

The ancient Greek sophist Gorgias compared the power of words to the power of drugs. More than two thousand years later, his insight is as compelling as ever. Words can persuade and deceive, comfort and inspire, alter the course of a life—or even the march of history.

Gorgias (483—375 BCE) hailed from Leontini in Sicily. He studied the art of persuasion—or rhetoric—under Corax and Tisias in nearby Syracuse and was also acquainted with the pre-Socratic philosopher Empedocles. In 427, he led an embassy to Athens to forge a defensive alliance against an overbearing Syracuse.

If Athens gave birth to philosophy, Sicily gave birth to rhetoric. Gorgias inherited the techniques of Corax and Tisias, the nominal founders of rhetoric, but transformed them into something that could dazzle audiences.

Indeed, Gorgias was something of a showman. He delighted in making unconventional, counterintuitive, or absurd arguments appear the stronger, and spoke in a florid, rhyming style that hypnotised all those who heard him. When in the theatre at Athens, he would say, “Come, propose me a theme!” He took great pride in his ability to defend any position, on any subject, and founded the art of extempore (‘off the cuff’) oratory.

In the Rhetoric, Aristotle characterises Gorgias’ style of oratory as ‘ironic’—and Gorgias’ opinions, if he had any at all, are hard to decipher. Rather than any positive philosophy, he offered an agnostic art of persuasion which he held to be of the utmost value.

In Plato’s Philebus, the sophist Protarchus tells Socrates: “I have often heard Gorgias maintain, Socrates, that the art of persuasion far surpassed every other; this, as he says, is by far the best of them all, for to it all things submit, not by compulsion, but of their own free will.”

Of Gorgias’ works, two short display speeches survive, the Encomium of Helen and the Defence of Palamedes, along with a fragment of a funeral oration and two paraphrases of a lost treatise, On Non-Being.

Words as Magic

In the Encomium of Helen, Gorgias sets himself the unlikely task of praising Helen and exculpating her for leaving Sparta with Paris and sparking the Trojan War. Gorgias argues that Helen could have been persuaded to leave in one of four ways: by the gods; by physical force; by the power of love; by the power of speech. But whichever way it was, she herself would have been blameless.

In defending Helen, Gorgias compares the effect of speech on the soul to the effect of drugs on the body: ‘Just as different drugs draw forth different humours from the body—some putting a stop to disease, others to life—so too with words: some cause pain, others joy, some strike fear, some stir the audience to boldness, some benumb and bewitch the soul with evil persuasion.’

A doctor’s diagnosis, a judge’s verdict, a declaration of love, a political speech, a prayer, or a promise may consist of nothing more than words, yet each can change the course of a life—even the course of nations and the march of history.

Perhaps this is why so many ancient cultures regarded words as sacred. In the Vedas, speech is revered as a divine power, and even personified as the goddess Vac. A similar idea can be found in the Bible, at John 1:1: ‘In the beginning was the Word, and the Word was with God, and the Word was God.’ In Genesis, God does not create the world with his hands, but by speech: ‘And God said, “Let there be light,” and there was light.’

As a psychiatrist, I am often reminded of Gorgias’ insight. Faced with a suicidal patient, everything may depend upon finding the right words at the right moment. A single sentence, if it is the right one, can alter a person’s entire outlook. Equally, a single sentence can break—or make—a career or a relationship.

The linguist may insist that ‘casting spells’ and ‘spelling words’ have different etymologies; the psychologist suspects that they spring from the same ancient intuition. If they had told us at school that we were learning magic, we would have paid a lot more attention.

Nothing Exists

In On Non-Being, Gorgias pushes his fascination with language to its absolute limit. Responding to the pre-Socratic philosopher Parmenides, who held that reality is one and accessible to reason, he parodies his arguments by turning each of them on its head: (1) nothing exists; (2) even if something did exist, nothing could be known about it; (3) even if something could be known, this knowledge could not be communicated to others; and (4) even if it could be communicated, it could not be understood. But as ever with Gorgias, it is far from clear whether these stood among his genuine opinions.

Gorgias spent much of his long life in Thessaly where he enjoyed the patronage of Aristippus of Larissa and Jason of Pherae. He taught Aristippus’ one-time beloved, the Meno who lent his name to Plato’s Meno, as well as the orator Isocrates, who came to rank among the Ten Attic Orators.

In his autobiographical Antidosis, Isocrates tells us that Gorgias:

…spent his time in Thessaly when the Thessalians were the most prosperous people in Hellas; he lived a long life and devoted himself to the making of money; he had no fixed domicile in any city and therefore paid out nothing for public weal nor was he subject to any tax; moreover, he did not marry and beget children, but was free from this, the most unremitting and expensive of burdens…

Having no wife or children, Gorgias died at the grand old age of 108.

Plato’s attacks ensured that the Sophists would long be remembered as clever tricksters rather than serious thinkers. Yet Gorgias deserves a more generous hearing. More than two thousand years ago, he recognised something we are still apt to forget: words do not merely describe the world. They shape how we experience it.

Every day we persuade, comfort, deceive, negotiate, inspire, forgive, and fall in love with nothing more substantial than sounds carried through the air. That is the nearest thing to magic that human beings have ever possessed.

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If you enjoyed this article, you might also enjoy The Gang of Three: Socrates, Plato, Aristotle, an engaging overview of the thinkers who shaped Western philosophy.

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Cicero (106–43 BCE), Rome’s greatest orator and one of the principal architects of classical rhetoric.

Learn the six classical parts of discourse used by Cicero—and discover why they remain one of the best ways to organise a speech or essay today.

Every good speech and essay has a structure. Yet few students are ever taught one.

For more than two thousand years, great speakers have relied on a simple six-part structure—a framework that stretches from Cicero to Churchill and remains just as useful today. Many Oxford students have told me that no one had ever taught them these six parts of discourse, despite years of essay writing. Yet, until surprisingly recently, they formed part of every educated person’s rhetorical training. Today, few people have even heard of them.

The six parts of discourse are, of course, just as useful for structuring essays as they are for composing speeches.

Table of the Six Parts of Discourse

Introduction (Exordium)

The exordium introduces your subject and purpose. It may also establish your authority for speaking or writing.

Above all, it should capture your audience’s attention. You might begin with a striking fact, an intriguing question, or a sense of urgency—but whatever your approach, make your audience want to hear more.

Keep it brief and clear. Never bore, confuse, or test your audience, and certainly not in the opening lines.

Winston Churchill’s first speech as Prime Minister begins:

I have nothing to offer but blood, toil, tears and sweat.

In just twelve words, he captures attention, establishes the gravity of the moment, and prepares his audience for what is to come.

Narration (Narratio)

The narratio provides the background your audience needs to understand the issue.

How did the problem arise? Why does it matter? What has already been tried? What does the evidence suggest? Have similar situations arisen before?

Important: Although the narration appears objective, it is also your first opportunity to frame the debate. The facts you include—and the order in which you present them—shape everything that follows.

Consider the difference between saying, “Taxes have risen by 2%” and “Investment in schools and hospitals has increased by 2%”. The facts may be identical, but the way you present them shapes how your audience understands them.

Division (Divisio)

The divisio is the turning point in your speech.

In effect, the division says:

This is the issue. This is why it matters. And this is how I intend to address it.

Like the introduction, the division should be brief. If it becomes too elaborate, it begins to feel contrived.

The rhetorical handbook Ad Herennium (c. 80 BCE) illustrates division with this dilemma from Greek mythology:

Orestes killed his mother, Clytemnestra; on that everyone agrees. But was he justified in doing so? That is the real point in dispute.

Proof (Confirmatio)

The proof is the heart of your speech. Here you present your arguments and support them with examples and evidence.

Aristotle distinguished between technical proofs, such as logical arguments (logos), and non-technical proofs, such as laws, contracts, witnesses, and authoritative testimony.

In the Rhetoric, he observes that ‘witnesses’ need not be living people. Homer, Hesiod, Solon, proverbs, and received wisdom can all serve as ‘ancient witnesses’. Today, we do much the same whenever we quote recognised experts or respected authorities.

Ancient witnesses can be appealed to indirectly, as when Barack Obama echoed Martin Luther King, who in turn echoed Abraham Lincoln, who echoed the King James Bible in the opening line of the Gettysburg Address of 1863:

Four score and seven years ago [i.e. 87 years ago] our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.

Refutation (Confutatio)

A persuasive speech anticipates objections.

The confutatio acknowledges opposing arguments before answering them. Ideally, it does so fairly and convincingly, though in practice speakers often exaggerate or caricature an opponent’s position.

Modern political campaigns often do exactly this. Terms such as ‘death tax’ or ‘dementia tax’ deliberately reframe an opponent’s proposal before it can be considered on its merits.

One particularly effective technique is concession (concessio). By conceding a limited point, you appear reasonable and fair while strengthening your larger argument:

Yes, that’s true. But the real question is…

Far from weakening your case, a well-judged concession often makes it more persuasive.

If your proof is weak, you might instead begin with a forceful refutation in the hope that no one notices the lack of argument. It is a trick as old as rhetoric itself—and one that is still surprisingly common.

Conclusion (Peroratio)

The peroratio brings your speech or essay to a memorable close.

It usually summarises your main arguments before ending with an emotional appeal or call to action.

President Franklin D. Roosevelt’s famous Day of Infamy speech, delivered the day after the attack on Pearl Harbor, ends with precisely such a peroration:

Hostilities exist. There is no blinking at the fact that our people, our territory, and our interests are in grave danger.

With confidence in our armed forces, with the unbounding determination of our people, we will gain the inevitable triumph—so help us God.

I ask that the Congress declare that since the unprovoked and dastardly attack by Japan on Sunday, December 7th, 1941, a state of war has existed between the United States and the Japanese empire.

When to Break the Rules

Many great speeches follow this six-part structure, whether consciously or intuitively. But the framework should never become a formula.

Once you’ve mastered its principles, they can also be broken.

Cicero himself ignored his own advice in the opening of the First Catilinarian, launching immediately into a passionate attack:

When, O Catiline, do you mean to cease abusing our patience? How long is that madness of yours still to mock us? When is there to be an end to that unbridled audacity of yours, swaggering about as it does now?

Nor must every speech contain every part. Aristotle regarded only two as essential: statement (narratio) and argument (confirmatio). Everything else is optional.

The six parts of discourse are not rules but tools. They provide a framework within which clarity and originality can flourish.

The aim is not to sound methodical but natural. Techniques such as using simple language, expressing uncertainty (dubitatio), or correcting yourself aloud (epergesis) can all help create the impression of sincerity and spontaneity.

Craft is something that you learn; art, that you unlearn.

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If you enjoyed this introduction to classical rhetoric, you’ll find many more practical ideas from Socrates, Plato, Aristotle, and Cicero in How to Think Like Plato and Speak Like Cicero.

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