The ability to identify logical fallacies in the arguments of others, and to avoid them in one’s own arguments, is both valuable and increasingly rare. Fallacious reasoning keeps us from knowing the truth, and the inability to think critically makes us vulnerable to manipulation by those skilled in the art of rhetoric. What is a Logical Fallacy?
A logical fallacy is, roughly speaking, an error of reasoning. When someone adopts a position, or tries to persuade someone else to adopt a position, based on a bad piece of reasoning, they commit a fallacy. I say “roughly speaking” because this definition has a few problems, the most important of which are outlined below. Some logical fallacies are more common than others, and so have been named and defined. When people speak of logical fallacies they often mean to refer to this collection of well-known errors of reasoning, rather than to fallacies in the broader, more technical sense given above. Formal and Informal Fallacies
There are several different ways in which fallacies may be categorised. It’s possible, for instance, to distinguish between formal fallacies and informal fallacies. Formal Fallacies (Deductive Fallacies)
Philosophers distinguish between two types of argument: deductive and inductive. For each type of argument, there is a different understanding of what counts as a fallacy. Deductive arguments are supposed to be water-tight. For a deductive argument to be a good one (to be “valid”) it must be absolutely impossible for both its premises to be true and its conclusion to be false. With a good deductive argument, that simply cannot happen; the truth of the premises entails the truth of the conclusion. The classic example of a deductively valid argument is:
(1) All men are mortal.
(2) Socrates is a man.
(3) Socrates is mortal.
It is simply not possible that both (1) and (2) are true and (3) is false, so this argument is deductively valid. Any...