Fallacy

noun

An opinion or belief based on incorrect or insufficient facts
A seemingly firm contention that is built on faulty reasoning or that contradicts facts
Flawed logic

Usage

Even with the unparalleled access to information that the Internet affords us, lots of us still, probably unknowingly, believe things that actually aren’t true. Just as the Internet can spread information, it can also easily proliferate misinformation. If we want our decisions to be fueled by reason rather than speculation, it is up to us to do our research and recognize ideas that might be fallacies.

A fallacy is a belief or idea that is formed with either a lack of accurate information, or unsound reasoning. In order for an idea to be a fallacy, rather than simply a contestable opinion, there must be objective facts that refute it. For instance, to strongly prefer Star Trek to Star Wars isn’t a fallacy, it’s simply a matter of preference. On the other hand, the belief that the Earth is flat rather than round would be a fallacy, since scientific evidence overwhelmingly suggests it isn’t. While fallacies often result from benign ignorance, sometimes they are irrationally embraced to deny unpleasant truths, though this latter case is often difficult to prove or distinguish from the former.

Sometimes, fallacy specifically describes an argument that relies on the kind of faulty reasoning that produces a mistaken or illogical conclusion. As with the primary meaning, fallacies can result from genuine error, but they can also be part of intentional efforts to misrepresent things. An argument can not only be a fallacy, but can also contain one. While an argument might accurately contend that something is true, it can do so with smaller points that are false. Since every part of an argument forms a part of the total reasoning, the more fallacies it contains, the more likely it is to be illogical as a whole. Fallacy can also refer to incorrect reasoning itself. If your logic is off, the process by which you form your beliefs or conclusions is fallacy (note that the article “a” is dropped).

In formal discourse and debate, you may encounter a logical fallacy, or formal fallacy. A formal fallacy is when a conclusion does not logically follow from a premise due to a flaw in the reasoning used to connect the two. This is different from an informal fallacy, where the logic that bridges the premise and the conclusion is correct, but the premise is erroneous. Consider this formal fallacy: “If a person’s name is Eric and the person has blonde hair, all people named Eric have blonde hair.” Despite the fact that the first two premises might be true of this particular individual, the resulting conclusion does not rationally hold. The truly logical conclusion should be that Eric has blond hair. But if Eric was actually wearing a wig to hide his baldness, one of your premises would be incorrect, making your conclusion an informal fallacy. While the conclusion of either type fallacy may nevertheless be true, the rationale behind a formal fallacy is always false.

Example: It’s a common fallacy that fortune cookies are authentically Chinese; they were actually invented in Japan, and the vast majority of them are manufactured and consumed in the USA.

Example: When he failed to produce evidence when pressed by the debate moderator, his argument was shown to be a fallacy.

Example: Her fanatical opinions were products of fallacy.

Example: In her paper, she committed the formal fallacy of “Appeal to Probability,” insinuating that her claim was true because it was likely to be the case.

Origin

First appearing in Middle English in the late-1400s to mean “deception” or “false claim,” fallacy comes from the Latin fallacia, meaning “deception, trick.” Fallacia derives from the Latin verb fallere, which means “to falsify or deceive” and is also an ancestor of the word fail. Related terms include the Old French word fallace and the Latin adjective fallax, both of which mean “misleading.”

Derivative Words

Fallacious: This adjective form of fallacy characterizes something, usually a claim or idea, as being misleading or untrue.

Example: While it is true that the government was running a deficit in that year’s budget, the claim by one party that it arose from the other’s policies was a fallacious political jab.

In Literature

From Ernest Hemingway's A Farewell to Arms:

No, that is the great fallacy: the wisdom of old men. They do not grow wise. They grow careful.

Hemingway here claims that the notion that age begets insight is inaccurate, or is a fallacy. Rather, he contends, what appears to be sagacity is merely excessive caution.

Mnemonic

A fallacy falls afoul of the facts
A fallacy fails to reflect reality
Fallacy: Fails in Accuracy