# Don't Say Fallacy When You Mean Lie

February 2, 2017

We live in a complicated time. Populism, “post-truth”, whatever you want to call it, with the information boom that the Internet has created, it’s easier than ever to spread misinformation, whether accidentally or on purpose. And for some time now, a lot of people have been warning about certain misinformation, sometimes with messages telling us to be careful not to use or believe certain “fallacies”.

But, what is a fallacy? Fallacy is a complicated word. It’s one of those words that you know but can’t really define. Most people associate “fallacy” with “falsehood”. They sound alike, and they’re apparently used as synonyms, so people have started using them interchangeably. But this, incidentally, is false.

A fallacy is not a falsehood. Bear with me for a minute: I know words end up meaning something based more on usage than actual definition, but this is actually a technical term, used in logic and mathematical reasoning, that has jumped to the general public. So, according to the technical definition, fallacy is a logically invalid argument or reasoning. Something being a fallacy doesn’t tell anything about the truthness of the premises or the conclusions, just about the argumentation itself. For example, the logical argument “Most people are right-handed, therefore the sky is blue during the day” is logically incorrect, yet its premise (most people are right-handed) and its conclusion (the sky is blue during the day) are both true statements. What is false, though, is that people being right-handed and the sky being blue are in any way correlated. This is, then, a fallacy.

Fallacies are, however, not so simple and not always so obvious. Typical fallacies use invalid transformations between different arguments rather than simple invalid arguments to prove a point. For example, the statement “If you are drinking an alcoholic drink then you are over 18, therefore if you’re not drinking an alcoholic drink then you are under 18” is false. The problem here is not in the two different logical arguments, but in the transformation applied to the first to deduce the second. It’s an incorrect application of the rules of the logical implication, in which you negate both the premise and the conclusion and arrive at a statement that seems right, but isn’t.

Ok, let’s get technical for a moment. That last reasoning can be written formally as:

It’s false, as stated by the $\not\Rightarrow$ symbol. The correct way of reasoning is by inverting the order of the premise and conclusion as well as negating them1, which would be written as:

That is: “If you are drinking an alcoholic drink then you are over 18, therefore if you’re under 18 you’re not drinking an alcoholic drink”. This is logically sound, regardless of the premise being true (which is true from a legal standpoint, but completely false from a realistic one). What this means is precisely that if the premise is true, then the conclusion is too. It is a logical statement by itself, and one that is true. If it were false, it would be a fallacy.

Of course, fallacies in daily life are not as simple or straightforward. You might have heard a few names of common fallacies: strawman, ad hominem, moving the goal post and such. These are a bit more complicated, and instead of explaining them myself, I’m going to show you a video from PBS Idea Channel that explains a few of them:

It should be noted that fallacies are not always attempts at manipulation, most of them are tricks or shortcuts our own brains do in an attempt to survive. Humans are pattern recognition machines, and we have, like any other animal, evolved to survive; our particular survival strategy is intelligence.

The most prevalent, probably most useful and likely most easily abused fallacy has a special name: inductive reasoning. Inductive reasoning is very important to survival, but it’s also logically wrong, and in today’s world it’s the cause of a lot of inequalities, prejudice and bigotry in general.

Inductive reasoning is, essentially, the overgeneralization of observations. It works by assuming that a repeated observed correlation is, in fact, an actual general correlation, and even one with causal connections.

An example: Spiders in the areas where humans evolved are generally venomous, so our brains started assuming all spiders are venomous. That’s inductive reasoning, and it’s wrong but incredibly useful. You might know now that in fact, not all spiders are venomous, but some are. By generalizing, we are more cautious and die less often. This, by the way, is the actual reason a lot of us have some level of arachnophobia: our own genetics doing inductive reasoning for us. It’s also how most of physics is done: We observe something, come up with a generalized explanation or mathematical formula that matches the observations, and then conclude that this formula is how things work. As long as we don’t find a counterexample and it has predictive power, we hold this as true. From a mathematical point of view, this is completely wrong, but it works and it’s the best we have.

However, in less scientific situations this doesn’t work as much. This is, for example, how people arrive to the conclusion that middle-eastern individuals are most likely terrorists: Western media depicts terrorists as being middle-eastern and gives very few examples of non-terrorist middle-eastern people in comparison. By inductive reasoning, our brains conclude that middle-eastern people will probably be terrorists, because that’s what we see. What worked for spiders and explained our arachnophobia, when applied to society, stops being useful and starts being plainly wrong, hurtful and, as evidenced by recent events, outright dangerous.

Intentionally or not, these kind of fallacious arguments are part of the current political discourse. Recently, people have started to identify them and talk about them, and the press is now talking about fallacies. It is important to identify and address fallacies, but sometimes people use the word too lightly. Sometimes, an argument is correct, but its premises or the data they reference are not. That’s not a fallacy: That’s a perfectly valid argument, but based on false data. Not a fallacy, but a lie. I believe this is because “fallacy” sounds a bit less serious than “lie” but they’re not the same thing. A fallacy might be intentional or not, and data can be false unintentionally, but more often than not these are not just random accidents, these are perfectly intended lies. The word lie indicates premeditation, though, use it carefully.

We’re sometimes too concerned with how we say things that we stop calling things by their names just in case. That’s how we started calling nazis “alt-right”, and even more recently calling lies “alternative truths”. Just call nazis “nazis” and lies “lies”, and stop with the sugar coating.

A typical example is presenting numbers of attendants to protests as facts. If you have ever peeked at the press after such an event, each and every newspaper has a different number. Granted, they’re estimates, but they present them as facts, which means that they’re intentionally misleading their readers, and therefore lying. They don’t usually publish their methods of calculating those numbers either, which usually involves a simple multiplication of estimated average space occupied times estimated average occupation density. How they come to these estimations is anybody’s guess, and the answer is probably more political than scientific.

To wrap up, it is important to note that neither using a fallacy nor using false data, intentionally or not, implies that the final conclusion is necessarily false. You can state that “the sky has a dome of blue color, therefore the sky is blue when illuminated”. It is true that the sky is blue when illuminated, but there’s no dome in the sky2! We’ve reached a true conclusion using false data. The same can happen using a fallacy.

This is, in fact, a fallacy on its own, which I’ll let Mike from Idea Channel explain again:

Be careful not to use a fallacy to call out a fallacy, though, because that might undermine your reasoning power in the eyes of others. Which is also a case of a fallacy fallacy, but whatever.

So, in summary: Call lies lies, and don’t use fallacies or lies yourself to make a point. However, don’t waste time using your reasoning power to combat someone that uses every single fallacy in the textbook, they’re just going to suck your energy and kill your motivation.

1. This is the contraposition in logic, a source of pain for a lot of students that, when explained with concrete examples, is very obvious.

2. This is, by the way, something that is still being questioned. In 2017. An article or two about actual, honest flat-earthers is coming sometime in the future, I promise.