In the course of any argument or discussion, good communicators need to know how to avoid logical fallacies. Logical fallacies weaken an argument by treating a false assumption as fact, but because many speakers and writers don’t take the time to consider the basis of their arguments, logical fallacies are fairly common in politics, business and even in interpersonal communication. This infographic about rhetorical techniques and logical fallacies (aka rhetological fallacies) by Information is Beautiful can help you understand these concepts better.
To understand logical fallacies, you should consider the six main categories of fallacy types: attacks, content manipulation, faulty deduction, inaccurate cause and effect, emotional appeals and mental appeals. While there are dozens of different fallacies, most of them fall into these six groups.
Attacks include ad hominems, in which the speaker attacks the other speaker rather than the counterargument. Unfortunately, this type of argument can be effective, but pointing out the attack will undermine its effectiveness.
Content manipulation is exactly what it sounds like: changing facts in order to suit the goals of an argument. The classic example is a confirmation bias. The speaker ignores facts that do not support or that directly oppose his argument.
Faulty deduction mimics a logical argument, but makes an ultimately illogical conclusion. The speaker might assume that a small sample size represents a whole group or that a general rule applies to all individual circumstances. Some faulty deductions are hard to spot, but they undermine an argument just the same.
Inaccurate or garbled cause and effect is somewhat similar to faulty deduction, but these arguments try to draw a clear link between an observation and an assumption when such a link isn’t necessarily there. An example is denying the antecedent. The speaker might say that “new refrigerators are cold, so the only way to get a cold refrigerator is to buy new.” This falsely assumes that there is one logical explanation for why a refrigerator would be cold–that is, it is a new refrigerator. All inaccurate cause and effect fallacies make a similar logical leap from a fact to a conclusion.
Mental appeals include the appeal to authority, which politicians frequently use. Saying something like, “that man must be guilty, because the police arrested him,” would be an example of an appeal to authority. The speaker is not addressing the core argument of the man’s guilt. Instead, he’s implying that the authority has expert knowledge of the circumstances and therefore must be correct. Other mental appeals make similar jumps in logic. An appeal to probability, for instance, assumes the inevitability of an event or circumstance without any reasoning. In an appeal to tradition, the speaker opposes change simply because it is a departure from established practices. Appeals to the mind appear to make sense at first, but they’re easily eliminated through logical counterargument.
Appeals to emotion are almost identical, but they focus on fear, love, hate and other strong emotions. An appeal to spite is a classic example. The speaker might say, “republicans hate the environment, so trusting a republican’s energy plan is ludicrous.” Usually, appeals to emotion are less overt, but they ignore the logical parts of an argument in favor of controlling the listener’s emotions.
All of these types of fallacies can quickly weaken a strong argument. In order to communicate clearly, you should remember to avoid these fallacies and know how to spot them in opposing points of view.