Logic for B.S. detection and getting to the truth

If you’re a liberal or progressive and have ever debated with anyone on the far-right, you may have noticed their arguments can seem irrational. Of course, it’s not just right-leaning people who think illogically, but any time you enter into or follow any controversial discussion, it helps to remember and identify the following fallacies.

Logic isn’t just overly intellectual nit-picking, as some people seem to think, but it’s an important way to avoid being manipulated and misled by deceptive assertions. When people use fallacies to debate, they deceive people and cloud any issue, whether consciously or not. Here are four commonly used informal fallacies:

(1) Argument from Ignorance: Some people argue that the inability to verify a given thing exists automatically means that thing does not exist. In his text on Logic, Robert Baum says, “The fact that a proposition has not been conclusively proved to be true establishes nothing but one’s inability to prove or disprove it.” The basic form of “argument from ignorance” is: “There is no evidence or proof that it is the case that X. Therefore, it is not the case that X.”

Baum clarifies by substituting “cigarette smoking causes cancer” for “X:” It would be fallacious to argue: “There is no proof that cigarette smoking causes cancer. Therefore, cigarette smoking does not cause cancer.”

The first part of the statement (the premise that cigarette smoking causes cancer) might or might not be true. However, the fact that there’s no conclusive evidence it’s true doesn’t prove anything.

(2) Appeal to Authority: People often try to make their case for or against something by quoting the opinion of an expert. It might be valid if the expert quoted is qualified regarding the question being discussed. However, if, for example, the authority quoted happens to be a physician working in a specific clinic, and that physician is cited as an expert on what goes on in clinics all over the country, (ones he might never have visited or even read about) the “appeal to authority” is fallacious.

The physician would have to be an expert in how most hospitals are run nationwide before he could logically be considered an expert in any way that matters or carries weight regarding the argument at hand. His expertise on his work in one specific clinic wouldn’t necessarily qualify him to speak knowledgeably about conditions in any others.

The basic form of “Appeal to Authority” is: “Person A is an expert on subject X. A says that such-and-such is the case about subject Z. Therefore such-and-such is the case about subject Z.”

(3) Ad Hominem, or Argument Against the Person: The usual way of defining this is using personal attacks in a debate as a substitute for addressing the other person’s assertion with facts or reason. In addition to “name-calling,” the use of ad hominem can include factual but irrelevant criticism of the other person in a discussion. Baum offers this form of Argument Against the Person: “Ad hominem attacks may point out a contrast between the opponent’s lifestyle and his expressed opinions . . . For example, ‘If Mrs. Jones really believed that the hospital is understaffed, she would work there as a volunteer.’ Such assumptions are, by themselves, quite clearly insufficient to support any conclusions as to . . . the true staff situation at the hospital.”

Mentioning the other person’s flaws isn’t an irrational act in itself. (In fact, it can be worthwhile.) Presenting the other person’s flaws for the purpose of proving a completely irrelevant point is what is blatantly illogical.

(4) The Straw Person Fallacy: This involves interpreting the other person’s position in a distorted, unfavorable way in order to more easily dismiss it. The distortion is a way of setting up a “straw person”—one that can be more easily knocked down than the person’s actual argument. Baum points out, “One of the basic ways to commit the straw person fallacy is to reduce a relatively complex argument to excessively simple form, in the process leaving out some of its key elements.”

It involves making a caricature of the other person’s actual argument, and then continuing to refute only that caricature, which the opponent doesn’t believe in the first place. This is a form of diverting attention from the topic at hand, or “throwing up gorilla dust” to distract from the real issue.

Of course, there are many more informal fallacies than the four mentioned here, and reviewing any reader-friendly book on the subject as a reminder of other examples can be worthwhile for anyone who wants to sharpen his or her b.s. detector. The purpose of understanding logic isn’t to ruminate excessively or over-intellectualize. The purpose, as Baum suggests, is to use wise judgment and make good decisions. A rudimentary understanding of logic can help people avoid buying into misleading assertions and more easily discern the truth in any given situation.