Logical Fallacies, Floodgates and Slippery Slopes

There’s so much flawed and downright dishonest thinking out there that it’s hard to know where to start.  This site has experienced its fair share of people trying to pull stunts based on dishonest or simply broken logic.  Some people have simply never learned how to think clearly, while others bend logic for their own cynical reasons or simply because they’re carried away on an unthinking wave of belief in some dogma.

logicIf I wrote about every logical fallacy that’s been tried in the comments here, the post would be so long you’d lose interest half-way through and go off for a drink, leaving me talking to myself.  Who wants that?   I don’t, so I’ll confine myself to a few examples here and there.

Right now, as the abortion bill makes its painful way through our parliament, we’re treated to the Floodgate argument and the Slippery Slope analogy, as if there really happened to be either floodgates or slopes, slippery or otherwise.  This is what happens when we abandon logic and instead rely on creaky old metaphors.   What gates?  What slopes?  There are none, except in the minds of the people who invoke them, and this leads to very faulty thinking indeed.

I particularly like the Slope and Floodgate false analogy because it embodies a few logical fallacies within itself.

First of all, it begs the question, which means that it assumes what it seeks to demonstrate.  Then it invites us to agree that there are, in fact, both floodgates and slopes.  It invites us to believe that one small step will lead to another until eventually we won’t be able to hold ourselves back and we’ll hurtle down that  slope like a coyote going over a waterfall.  The Floodgates trick relies on much the same sleight of hand.  We have to agree that there are such gates.  We have to accept that they’re holding back a great flood and we have to buy into the mental image of a biblical deluge when they fall open.

Except that, of course, neither stratagem proposes any mechanism to describe how that will happen.  Instead, it relies on the simplistic cartoonish understanding of physics  we all carry inside us from childhood.  You might call it the Roadrunner school of logic.

This being Ireland, of course, Floodgates seem to apply almost exclusively to matters of a sexual or reproductive nature and it seems to be the same right-wing groups who believe in them.  They warned about opening the floodgates to divorce and what happened?  Nothing.  Those whose relationships were already broken simply went their separate ways with some sort of legal clarity.  Everyone else stayed married.  Astonishingly to anyone born in the 80s, they even shouted about floodgates if contraception was legalised.

I say almost exclusively, but there is, these days, an especially nasty use of the term by those opposed to immigration, and of course, these characters are speaking to a constituency that has no history of rational thought.  Now we’re into violent populism, a place where false logic is the demagogue’s friend.  At the extreme end, you could think of the analogies made by dictators through the decades but I don’t want to go there right now, since this is mostly intended to be about the skips and jumps made by normal people and by a few fringe nutters in Ireland.

Back in the Fifties, the Floodgate and Slippery Slope theory went out under a different name.  In those days it was called the Domino theory, and it gave us the Korean War and the Vietnam War, both of which were helped by yet another logical fallacy, the Big Lie which also gave us the Iraq invasion.  More about that later.

Old Lord Denning covered himself in disgrace towards the end of his career when, at the age of 81, he relied on the logical fallacy, argument from consequence.  In 1980, Denning delivered a judgement refusing the Birmingham Six leave to appeal their convictions because if they won, it would mean that the police were guilty of perjury; that they were guilty of violence and threats; that the confessions were involuntary and improperly admitted in evidence; and that the convictions were erroneous.   That was such an appalling vista that every sensible person would say, “It cannot be right that these actions should go any further.  

It was an appalling judgement, utterly devoid of rational logic and a blight on the reputation of a man who began his career as a first-class mathematician before turning to law.  In his younger days, Denning recognised nonsense when he saw it, effortlessly puncturing one of the most irrational canards commonly produced during past abortion and divorce debates in Ireland.

Hard cases make bad law.  This is such a cliché now that not even the Ionabots are mouthing it, but in its day, every hack in the country had it on the tip of his or her tongue.  What does it mean?  It’s a heartless ideology that suggests law should not be influenced by compassion, and it’s patent nonsense, thoroughly discredited but still heard occasionally even though the reality is that bad law makes hard cases.

Here’s what Denning said about it in 1974:

Mr. Balcombe … started off by reminding us that “hard cases make bad law.” He repeated it time after time. He treated it as if it was an ultimate truth. But it is a maxim which is quite misleading. It should be deleted from our vocabulary. It comes to this: “Unjust decisions make good law”: whereas they do nothing of the kind. Every unjust decision is a reproach to the law or to the judge who administers it.

QED.  But of course, if you wished to discredit this judgement, you could call up another logical fallacy by relying on an ad hominem argument, attacking Denning’s personal integrity.  You could quote the appalling vista judgement six years later and suggest that his judgement was already impaired, even though there would be no logical basis for such an assumption.

The beloved ad hominem never goes out of fashion, for the very good reason that it appeals to something atavistic in us, some dark desire to stick the knife in, or perhaps the fang.  We can’t help it, as animals, but it needs to be resisted constantly because, as has been pointed out, even the very worst of us is capable of being correct.

What time is it, Adolf?

Four o’clock.


There’s a logical fallacy called Appeal to Authority that crops up on Facebook all the time, often with ludicrous results.

The definition of insanity is doing the same thing over and over and expecting different results.” — Albert Einstein.


Wrong.  Einstein said no such thing.

And he never said Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.

Or, Logic will get you from A to B. Imagination will take you everywhere.

He never said these things, or almost anything else attributed to him on Facebook and yet, to the common understanding,  Einstein is the single transferable genius, the touchstone for wisdom and the very embodiment of incisive logic.  We love our learned professors, especially if they happen to have an endearing dottiness about them even though in real life there was nothing dotty about Albert Einstein.  We love to quote authority, as if that made our assertions correct.  Thus we hear TDs and county councillors, many with little or no formal education, explaining how they were recently discussing the same-sex marriage issue with four eminent psychiatrist friends and they all agreed the law was a mistake.

Three things here.  First, some of these people would be hard put to discuss the winner of the 3:30 in Haydock.  Secondly, no experts would waste their time discussing anything with a shiny-suited fool and thirdly, even if a hundred experts agree with you, that doesn’t make you right.  This is an appeal to false authority.

The Ionabots use a variation on it, appealing to authority but subtly changing what that authority said to suit their own ends, as we saw in their misleading submission to the Constitutional Conference, when they deliberately omitted a vital preamble to a paper written by an American research group, Child Trends.  That organisation was finally forced to write to the secretary of the convention in order to correct the false impression created by the Iona people.  There are many variants on this fallacy.

Doctors agree.  All studies prove.  And that subliminal appeal to the Irish sense of inferiority : International research shows …

This tactic is commonly  employed along with another cynical false tactic: repeating the mantra until it sticks.  Keep saying it over and over even when you’ve been utterly demolished in debate.  Don’t worry if you lost comprehensively on Prime Time.   You can always go on Vincent Browne and repeat the same lie.  Someone is bound to believe you and if you keep doing it often enough, you’ll make progress.  Never mind that what you’re saying is untrue.  That’s not the point.

It’s all aimed at the peasant in us, and it works, if you don’t know what they’re up to.

Who accomplished this most spectacularly in recent times?  That prize must go to Dick Cheney, a master of deception, who employed several logical fallacies together in order to prepare the American people for the invasion of Iraq.

Cheney in his speeches used a combination of the Big Lie – previously employed following the Gulf of Tonkin incident to precipitate the Vietnam War — repetition and the proximity smear.  Thus, in order to persuade Americans that Saddam Hussein was responsible for the 9-11 attacks, in the absence of evidence Cheney had to resort to other tactics.  He had to sell the Big Lie by repeatedly associating Iraq with 9-11 in the same breath and that’s exactly what he did.  Despite the fact that a Vice President has no executive or policy role, Cheney provided the vanguard for the Neocons who pulled GW Bush’s strings.  Relentlessly, he hammered home the same message, by the simple expedient of evoking 9-11 and immediately mentioning Iraq.  As far as the Great American Public was concerned, there be dragons and one rag-head is the same as any other, even though Hussein and Bin Laden were sworn enemies.  Even today, as many as four in ten of all Americans still believe Iraq was behind the attacks on New York and Washington.

That brought us to the ludicrous proposition that we must support the troops, even if they’ve been sent to prosecute an unjust war.  This was perhaps one of the most pernicious falsehoods ever propagated and yet it gained huge traction in the US, a country where the military has become fetishised by generations of jingoistic and propagandist movies.  It came to the point where supporting the troops was more important than asking if they should be there in the first place, and to the absurdity that the very presence of the US military anywhere in the world was enough to legitimise that action.

This technique continues in use here in Ireland, in a far more parochial, but essentially identical way.  Invent a lie.  Keep repeating it.  The fetishising is more subtle, in the form of nebulous concepts such as The Family and The Unborn, but the lust for power is the same.

Of course, we couldn’t have a discussion about broken thinking, dishonesty and manipulation without mentioning the frauds and charlatans attending the alternative medicine industry, a bunch of people whose creativity and imagination is beyond question, even if grossly misdirected and sometimes combined with sheer bone-headed stupidity.  After all, only a homeopath would try to treat you with water that had once contained a piece of the Berlin Wall.  Only a homeopath would try to convince you that water containing nothing at all can cure your illness.

In order to bolster this absurd but profitable industry, the frauds, quacks and chancers need to call up the big guns of logical fallacy, so let me tell you about some of these evasions and tricks.

My personal favourite is the appeal to antiquity, the idea that ancient knowledge is superior to carefully-applied study using the most advanced techniques available.

For thousands of years, herders in Bhutan have used yak shit to treat cancer.  Really?  And have they kept careful records to establish how well it worked?  Did they pass their results to herders in Tibet for careful scrutiny?  Were they able to cure cancer over and over again using yak shit?  What kind of cancer, since there are so many unrelated variants?

You see, the ancients really aren’t all that great an authority for appealing to.  After all, didn’t some of these same ancients believe that the world rested on the back of a giant turtle?  Did they not believe that the sun orbited the earth?  Did they not, in fact, imprison Galileo for suggesting the opposite?  Did some of them not think it was possible to sail over the edge of the planet?  How come the endlessly-wise ancients didn’t eradicate smallpox and tuberculosis?  And then those pesky scientists came along and worked out how vaccination might eradicate diseases while at the same time, old Hahnemann, the father of homeopathy, was banging a bottle of water against a leather cushion and calling it science.

And then comes the burden of proof problem.  As has often been said, what can be asserted without proof can be dismissed without proof.  If somebody tells you that a bottle of water can cure your gout, it’s not your responsibility to disprove it.  The onus is on the person making the claim to support it with facts.  This fallacy frequently goes hand-in-hand with the argument to the future, which is utter nonsense: science can’t explain it but it works and we’ll understand it in the future.  No.  First you have to produce evidence that your bottle of water cures anything.  Peer-reviewed double-blind trials.  A sound, logical basis for your claim.  Anything else is simply passive-aggressive sulking.

There’s a peculiarly modern form of fallacious argument that relies on the appetite for popular science, and this leads to a delicious paradox when some people try to promote alternative medicine.  The quacks and frauds love to quote something they call energies without ever defining what they mean by that term, apart from a vague hand-waving touchy-feely sort of idea, but they excel themselves when they talk about quantum effects, perhaps one of the most exquisite hijackings ever of a scientific concept by a profoundly unscientific, anti-intellectual movement.

In the quack medicine field, science ceases to be a rigorous examination of facts and is instead reduced to a set of appeals: to antiquity, to authority and to widespread belief.  If enough people choose to believe that yak shit can treat cancer, then it must be so, regardless of the evidence, or lack of it.

There’s a lovely one called the fallacy of division, which asserts that whatever is true of the whole is also true of every part.  Therefore, for example, if a person is a conscious being, then every atom making up that person is also a conscious entity.  Every atom in your body has a mind of its own.  This is like saying that you can play music using only the volume knob of your stereo, but logic has never been a huge thing in alternative circles.

It’s also a bit like saying that eight fertilised cells are a human being, which by a commodious vicus of recirculation brings us back to where we came in.

I haven’t time to deal with this issue as I’d like to, but I’m grateful to a commenter earlier this evening for using yet another form of fallacious reasoning: moral equivalence.






11 thoughts on “Logical Fallacies, Floodgates and Slippery Slopes

  1. Social change – not destroying society since time immemorial.

    Excellent piece.

  2. Another excellent post Bock.
    Somewhat related, you should like this “Cognitive Bias” song.

  3. Two swallows do not make a summer; but two “miracles” are enough evidence to elevate a Pope to “Sainthood”–whatever that is. Some wise wag in our popular press recently declared that theology was the queen of sciences although I would wager that most self respecting mathematicians would not agree. Enough about the Voodoo–thank you for this post and the logical thinking; I’m sorry to say Bock that I don’t think you have any future as a Gombeen politician. Then again we have an unhealthy surplus of that breed.

  4. A majority of pre-med Harvard students with a strong high school physics background thought that in a head- on collision, a heavy truck would exert a greater force on a light truck than the light truck
    on the heavy truck. Actually, the forces have the same magnitude.
    Interestingly, even after taking and excelling in a first year calculus based physics course, the improvement in the student’s conceptual understanding of physics was surprisingly low. The conceptual testing involved questions like the one above, I.e. questions with no numerical content. These student’s mindsets were still locked in Aristotelian notions of motion, despite their high academic ability and privileged education. It seems that implementing improvements in the general public’s understanding of basic scientific concepts, as well as critical and statistical thinking etc. may be a long way off.

  5. you can teach people all the formal analysis you want, but if they don’t get the idea in the first place, no amount of mathematics will help.

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