Lecture 4:
Logical Fallacies

Sometimes, people will use reasoning to try to convince you which is flawed or false because it violates the rules of logic. There are many ways to violate rules of logic; they are called "logical fallacies." There are dozens of logical fallacies. Listed below, with examples, are only a few. Once you start looking for them, you will find them everywhere: in politics, in advertising, even in your own thinking. We all fall prey to these fallacies once in a while, but being conscious of them can make us less vulnerable.

Equivocation occurs when a word has one meaning in one part of the argument and another meaning in another part. Examples:

Non Sequitur occurs when the conclusion does not follow from the claim. Examples:

Post Hoc, Ergo Propter Hoc occurs when people assert that because two events occurred closely together in time, one event caused the other. Examples:

Hasty generalization occurs when people assume that because one or two examples are true, all similar examples are true. Examples:

Slippery Slope occurs when a person argues that a whole course of actions will inevitably result from one action. The argument is that once you allow one thing, a whole flood of other, disastrous, things are sure to follow. Usually this argument is made without any evidence to show that those other disastrous things will actually follow. Examples:

False Analogy occurs when you use an analogy to make a point. An analogy is a comparison between two similar items. Analogies can be useful, but their weakness is that two things are never really the same. False analogy occurs when the two things being compared appear similar but are really very different. Examples:

Straw Man occurs when a person creates a weak, oversimplified, or exaggerated version of his opponent's argument, refutes it, and then says he has proven his opponent's argument wrong. Examples:

Begging the Question occurs when someone draws a conclusion based on a premise which actually needs proof. Here's a sample argument: Everything in the Bible is true. The Bible says that Noah built an ark. Therefore, Noah's Ark really existed. The problem with this argument is that "Everything in the Bible is true" has not been proven. The conclusion is based on a premise which needs to be proven. Examples:

Either/Or occurs when a person says there are just two choices when in reality there are many more. Examples:

Oversimplification occurs when it is assumed that there is a single, simple cause of an outcome or a problem when in reality there may be many causes or elements. Examples:

Tu Quoque is Latin for "you too." Pronounced too-kwo-kwee. You avoided having to engage with criticism by turning it back on the accuser - you answered criticism with criticism. This fallacy is also known as the appeal to hypocrisy. It occurs when a person rejects an argument because the person making it doesn't follow his own advice. It's annoying when a person gives you advice he doesn't follow. But that doesn't mean his advice is bad. Examples:

Appeal to Ignorance occurs when a person argues that his lack of evidence shouldn't invalidate his argument, because there's way to now what that evidence is. Examples:

Ad Hominem is Latin for "against the man." It occurs when an opponent attacks the person making an argument, rather than attacking the argument itself. This is common is political contests. Examples:

Appeal to Fear occurs when a person tries to persuade someone to do something by making them afraid of what will happen if they don't do it. It often looks like this: if you don't accept X as true, something terrible will happen to you. Therefore, X must be true. Examples:

Bandwagon occurs when someone tries to convince you to do something because "everyone else" is doing it. Examples: