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Fallacies

A rough and ready outline of some common logical fallacies. For a full list, look at Nizkor.org’s Fallacies Page and the Skeptic’s Dictionary.

Begging the Question

It is a common assertion in public debate that one’s opponent is “begging the question”. Their statement, you say, “begs the question of X”. This is a fallacious use. When most people say that something “begs the question”, what they mean is that it raises a question. This is perfectly fine. Statements ought to raise questions. Begging the question is different: begging the question is when one reasons circularly – that is, the conclusion of the argument is already in the premise of the argument.

Guilt by Association

Guilt by association is when one thing is claimed to have the properties of another because of an irrelevant association.

“Eugenics is bad because Hitler used eugenics.” is an example of guilt by assocation. Most reasonable thinking people agree with the conclusion that eugenics is bad. But it is not bad because Hitler supported it. Why?

“A punctual train system is bad because Hitler made sure the trains were punctual.” A similarly irrelevant association. Nobody argues that punctual trains is bad because Hitler made the train system in Germany punctual. Hitler was also an art student, a decorated World War I veteran, possibly a vegetarian (some historians doubt it), a charismatic orator and lived in Vienna – but arguments pointing to these attributes are irrelevant.

Sorites Fallacy

The Sorites fallacy is a complicated one: it exists because of the problem of vagueness, specifically vagueness regarding collections of sortals. The classic example is that of a heap or a crowd. Imagine you have a grain of a substance like sand, sugar or salt. This is not a heap as it is only one grain. Now imagine you have a heap of a few thousand grains. This is obviously a heap. And if you take a grain off the heap, it still remains a heap. As you keep taking more and more grains off the heap, at some point it must surely stop being a heap. But when?

A political example: the world is not divided into clear categories of rich and poor. Income and wealth exists on a continuum and many people exist in the comfortable middle of the continuum – they are neither on the breadline nor are they driving a Lambourghini down Mayfair. This continuum doesn’t mean that there is a difference between the worst off in society and the best off, and it certainly doesn’t mean (for instance) that one cannot take the position that we have a moral duty to help the worst off in society. To do that, one might need to draw an arbitrary line (say, everyone earning under £15,000 per year).

The Sorites fallacy is committed when someone uses the fact that a continuum exists to cast doubt on there any substantive point made about the subject.

This is Something!

As fallacies go, this is more of a rhetorical trope that borders on an informal fallacy. It is very easy to identify:

“Everyone agrees that we must do something about Problem X.”
“This is something.”
“Therefore, we ought to do this.”

This rhetorical trope is problematic when it is invoked in response to the suggestion that a measure doesn’t actually solve the problem it purports to solve. As a response it doesn’t work because it doesn’t adequately respond to the problem raised. It dismisses it without providing any good reason. As an argument in itself, it doesn’t work because it justifies any policy. Consider:

“Everyone agrees that we must do something about the mass disobedience to the ban on hunting with dogs.”
“Eating jelly is something.”
“Therefore, we ought to eat jelly.”

It is a perfectly valid argument: the premises support the conclusion. It is therefore not a formal fallacy. But it is an informal fallacy because it proves too much. Anyone who agrees that we ought to do something about people disobeying the hunting ban should agree that they ought to eat jelly. Someone may object at this point and say “well, the something needs to be relevant!” Exactly. That is my point. One needs to show in one’s argument that what one is proposing is relevant and effective to the aim that is expressed in the first premise.

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