Some Logical Fallacies

Fallacies are errors in argument, intentional or accidental, that misrepresent the nature of an argument and mislead listeners/readers. Most fallacies either evade the argument or oversimplify it. Here is a partial list of some of the most common fallacies:

The Slippery Slope: asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question. In most cases, there are a series of steps or gradations between one event and the one in question and no reason is given as to why the intervening steps or gradations will simply be bypassed. This "argument" has the following form:

Event X has occurred (or will or might occur).
Therefore event Y will inevitably happen.
This sort of "reasoning" is fallacious because there is no reason to believe that one event must inevitably follow from another without an argument for such a claim. This is especially clear in cases in which there is a significant number of steps or gradations between one event and another.

Examples: 1) We've got to stop them from banning pornography. Once they start banning one form of literature, they will never stop. Next thing you know, they will be burning all the books! 2) If we legalize gay marriage, then soon polygamy and all sorts of other abominable practices will be legal.

Begging the question: assumes a debatable part of an argument is already agreed upon. Example: the heavily polluted Cape Fear River can't provide adequate drinking water for Wilmington (assumes river is heavily polluted).

Non sequitur: occurs when a conclusion doesn't logically follow its premises. Example: because you borrowed my psyche notes, I flunked my Spanish test (no connection between premise and conclusion).

Red herring: introduces unrelated information to distract the audience's attention. Example: you should just extend the due date since the Panthers are playing tonight (the Panthers' game is an unrelated distraction from the real issue).

False authority: using a non-authority in an appeal to authority. Example: Britney Spears recommends we give end-of-year tests to all school children (Britney Spears isn't an education expert).

Bandwagon: appeals to people's desire to conform to the larger group. Example: you should try marijuana because over 50% of Americans have tried it (the fact that many people have done something doesn't automatically make that something justifiable).

Ad populum: inappropriately appeals to people's general feelings of love, hate, patriotism, fear, etc. Example: if you're a true-blooded American you won't criticize my ideas (doesn't address the merits of the ideas).

Ad hominem: distracts from argument by attacking the person or persons making the argument. Example: don't listen to Bill Clinton's advice on economic policy because he cheated on his wife (personal attack distracts from merits of suggestion).

Hasty generalization: reaching a generalized conclusion from too little evidence. Example: Susie didn't say hello to me when we passed in the hallway. She hates me! (there isn't enough evidence to reach the conclusion).

Post hoc: assuming that since A happened before B, A must have caused B. Example: After eating a cheeseburger, I wrecked my car. The cheeseburger must have made me wreck my car (no clear connection between A and B).

False analogy: making implausible comparisons to prove a point. Example: Teachers are like doctors; so don't grade my paper, just heal it (not sufficient evidence to support comparison).

Either/or: assuming there are only two conclusions that can be reached. Example: I'll either get an A in this class, or I'll flunk (doesn't acknowledge other possibilities).

Straw man: ignores a person's actual position and substitutes a distorted, exaggerated or misrepresented version of that position. This sort of "reasoning" has the following pattern:

Person A has position X.
Person B presents position Y (which is a distorted version of X).
Person B attacks position Y.
Therefore X is false/incorrect/flawed.

Example: Senator Doe believes that we should have a program that will offer undocumented immigrants in our country a path toward citizenship. I do not believe that we should just hand this country over to illegal aliens.

Partial Source: http://cfcc.edu/SACS/QEP/documents/BasicsofArgumentandRhetoric.doc
See more logical fallacies at: http://www.nizkor.org/features/fallacies/