Arguments have Logic

Logic is the science or art of reasoning. Formal logic is a system of inference, generalization, and demonstration, but at its simplest, saying that an argument has good logic means, that it makes sense – that the claims lead you step by step to the conclusion. Fallacies make their way into arguments and try to present themselves as logic, however, they actually lead unsound conclusions and make arguments weak.

Syllogism This poster uses a classical form called syllogism that consists of a major claim, a minor claim, and a conclusion. The unstated major claim here is that people who fish tell lies, the minor premise is that the speaker fishes, and the conclusion is that the speaker tells lies. Most arguments that you encounter, however, are much more complicated and many times use faulty logic. Logical fallacies appear convincing, but when you take a closer look at them, they don’t make sense at all.

Non Sequitur This is an example of a non sequitur fallacy: Latin for “does not follow”. Look for claims that have too much of a gap between the data and the claim. This poster claims that you should get your tuberculosis test right away because good grades follow good health. While it may be true that illness can hurt your performance in school, the data is irrelevant to whether or not good health will result in good grades. Cadbury Ad

Ad Hominem Responding “against the man” instead of responding to the argument itself; usually this fallacy implies attacking the character of the arguer, which has nothing to do with the issues being argued. In this cartoon, the woman attacks the man literally instead of responding to his argument that it’s the thought that counts when giving or receiving gifts.

Slippery Slope Fallacy arguments, as their name implies, are like steep, ice-covered hills: Once you start down, you can’t stop – with some extreme and negative result. This cartoon, for example, suggests that giving your employees a casual dress day will have them coming to work looking like complete slobs. Anti Jim Walsh

Bandwagon Appeal These fallacies offer as support the fact that a famous person or many people already support it. (Unless the supporters are authorities, their support is irrelevant)

Begging The Question To beg the question is to argue in a circle; to offer a claim that assumes the validity of the claim. Here this headline, published after the Red Sox won the 2004 World Series, claims that they were destined to end the Curse of the Bambino- it begs the question because they already had.

Hasty Generalization Makes claims based on insufficient or unrepresentative data. Making assumptions about a whole group or range of cases based on a sample that is inadequate (usually because it is atypical or just too small). Stereotypes about people ("frat boys are drunkards," "grad students are nerdy," etc.) are a common example of the principle underlying hasty generalization. PETA