21 Common Logical Fallacies. Incorrect Reasoning in Argumentation. Common Errors in Reasoning.

Here are Top 21 Logical Fallacies:

Common Fallacies

Ad hominem

Attacking your opponent, rather than his argument or evidence. This is often used by people to draw attention away from their own insufficient evidence or faulty arguments. The intent is to discredit an argument by discrediting the person arguing, even though the two are not directly correlated (an unpleasant person may have a perfectly valid argument).

Appeal to ignorance

Drawing a conclusion from a lack of evidence, or using a lack of evidence to support a claim. For example, there is no evidence one way or the other about the existence of God. But both sides of the issue use this lack of evidence to support their claims for and against the existence of God.

Appeal to popularity (Ad populum)

Trying to validate or justify a claim or argument by appealing to popular opinion; believing that something must be true because it is widely believed to be true. However, popular belief does not a fact make. People have accepted as common wisdom any number of complete fallacies, such as the flat earth or the idea that traveling at speeds of over fifteen miles per hour would be fatal.

Appeal to questionable authority

Resting the validity of an argument on the opinion of someone who does not have the skill, training, education, or expertise required to give a valid opinion in that area. For example, relying on a non-electrician to validate the quality of electrical work.

Begging the question

A fallacy in which the underlying evidence for the reasoning is assumed within the reasoning. For example, “Stealing is wrong, therefore taking extra sugar from the diner is wrong.” In this argument, the premise—that taking extra sugar from the diner is stealing—is assumed, but never addressed. Since the premise has not been established as fact, the argument based on it is null and void. This can be a very difficult fallacy to understand and to spot in action. It is very easy to simply accept the underlying assumptions as fact.

Conjunction fallacy

The belief that specific conditions are more probable than general ones. Often used in advertising, since a specific claim (four out of five doctors prefer) is more believable than a general one (doctors agree).

Either/Or (false dilemma or false dichotomy)

Giving or assuming only two options when in reality many options may be available.

Equivocation

Using a word that has more than one meaning in an argument. When an alternate meaning is put into play, the argument no longer makes any sense. For example:

• All men are created equal
• Women are not men
• Therefore, women are unequal

In this sense, the word “men” was originally used to infer “mankind,” but in the second instance the meaning is changed to mean male humans. In this way, it is easy to twist the meaning of a word to derail or falsely win an argument.

Explaining by naming

The fallacy that because you have labeled something, you have explained it.

Gambler’s fallacy

The belief that unique random events or results are caused by or affected by prior unique random events. For example, the belief that a “lucky run of the dice” will positively or negatively influence later rolls, when in fact each roll is individually random and in no way affected by other rolls, or that because a specific string of numbers won in one lottery, it is more likely to win again, when in fact each winning series of lottery numbers is uniquely random and not influenced by any other series.

Glittering generality

Using vague, positive descriptions or emotional appeals to entice someone to approve of something they might disapprove of upon closer, rational examination. “No one will get hurt…it’ll be fun!”

Hasty generalization

Assuming something to be true for all members of a group because it is true for some of them. “That manager is great to work with. All the managers at that firm must be great to work with.”

Ludic fallacy

The tendency to apply the simpler probabilities of games or models to infinitely more complicated real-world situations; mistaking the model for the system. For example, assuming that because you often win at Monopoly, you should be able to get rich in the real estate market. Also, assuming that something has a far simpler probability structure than it does by ignoring real-world complexities.

Red herring

Introducing an unrelated argument in such a way that it appears related in order to change the subject to one more easily winnable or move the discussion to one more favorable for yourself.

Post hoc

Falsely associating two unrelated events as cause and effect. A new law passed making it illegal to beg on the street. Crime went up. Therefore, outlawing beggars increases crime.

Slippery slope

The belief that one action will set off a cascade of further actions (usually, but not necessarily, negative), when in fact there are safeguards or systems in place to prevent this cascade.

Searching for perfect solutions

The belief that a solution should not be adopted because it does not solve every aspect of a problem. Often used by antagonists as a pseudo-legitimate way to scuttle perfectly good solutions they don’t like. In reality, a good solution covers most of the bases, and the remaining issues can then be dealt with one at a time, as needed.

Straw person

Distorting or misrepresenting an opponent’s position to make it easier to attack. By doing so, you wind up attacking a position that was never proffered. For example, if someone says that in times of famine, food rationing makes sense, to distort that argument you claim that your opponent supports starving children in order to feed the rich (which no sane person would support) is to use a straw man argument.

Texas sharpshooter

Stating or altering your hypothesis after you’ve collected the data. For example, changing or taking a political stance after viewing poll results.

Weak analogy

Drawing upon a poor analogy to support a claim. For example, saying that because we have hungry people in North America, we shouldn’t send aid to a famine-stricken foreign country. In reality, the analogy is weak because even the poorest people in North America usually have access to at least some food (through food pantries, government programs, soup kitchens, etc.) when there may be little to no food at all in the other country.

Wishful thinking

Assuming something to be true because you want it to be true. When wishful thinking forms the basis of an argument, the entire argument becomes invalid.