Figuring out what’s fact and what’s not, or where the grains of truth may lie, in a media-saturated culture can sometimes be difficult. Between entertainment “news” and email “elerts” about everything from government conspiracies to cancer cures across a plethora of printed and virtual media forwarded faster than the speed of light, it becomes more critical than ever to be able to identify the logical fallacies that blur the line between opinion and fact.
Logical fallacies are errors of reasoning that can be formal (deductive) or informal (inductive) and typically fall into about ten or twelve types within three basic categories :
- Fallacies of Relevance
- Fallacies of Ambiguity
- Fallacies of Presumption
Learning to identify the most basic errors of reasoning is critical to everything from being an educated consumer to appreciating and exercising responsible First Amendment rights, to making informed decisions about health and well-being.
Inductive or Deductive Reasoning
For the purposes of understanding logical fallacies , it’s important to understand that an argument, in this case, is not a disagreement between two or more people, but rather the statement of one or more premises given in support of a conclusion. In order to realistically evaluate an argument, one must have tools for deciding whether premises are true or false, based on factual statements or on personal opinions.
First, it helps to know whether an argument is based on inductive logic – moving from a set of specific premises to support a general conclusion – or deductive logic – moving from general statements to a specific conclusion. It’s also important to understand that a deductive argument can only be “valid” or “invalid,” as opposed to “true” or “false.”
An example of an inductive argument might be:
- Every crow in a random sample of 100 crows is black.
- Therefore all crows are probably black.
A classic example of a valid deductive argument can be:
- All men are mortal.
- Socrates is a man.
- Therefore, Socrates is mortal.
If the premises in an inductive argument provide a reasonable degree of support for a conclusion, the argument is said to be good, or sound. A deductive argument is considered valid if all the premises are true, and invalid if one or more of them is false.
Identifying Logical Fallacies
False premises can lead to erroneous, misleading and sometimes dangerous conclusions. Fortunately, there are good clues as to the validity of statements. According to Garth Kermerling's Philosophy Pages, many of the most common logical fallacies were identified by Medieval and Renaissance philosophers and logicians who gave them Latin names that are still in use today. One of the most familiar is the ad hominim argument, a type of “Fallacy of Relevance” that literally means “against the man,” and consists of discrediting an idea because of the supposed disreputability of the source.
An example of an ad hominim argument might be:
- Sen. Smith is opposed to raising the drinking age.
- But everyone knows that Sen. Smith is a fool.
- Therefore the legal drinking age shouldn’t be changed.
The opinion about Sen. Smith, even if substantiated, is irrelevant to the conclusion of the argument because it fails to focus on the facts of the issue itself.
Other common “Fallacies of Relevance” include:
Appeal to Pity (argumentum ad misericordiam) consists of trying to persuade through a suggestion that unfortunate circumstances will befall the speaker or others;
Appeal to Emotion (argumentum ad populum) is among the most pervasive of argumentative fallacies, appearing in everything from popular media advertising (“Men with dyed hair will have more dates”) to politics (“Smart voters know the president has a socialist agenda, therefore no intelligent person would support her policies.”).
Fallacies of Ambiguity
Fallacies of ambiguity are based on imprecise language use. They include things like:
- Equivocation, or the misleading use of a word: "A feather is light; What is light cannot be dark; Therefore a feather cannot be dark."
- Amphiboly, or poor grammatical sentence construction:" A motorist struck a man who was jogging with his car. Therefore it’s unsafe to jog with a car. "
Fallacies of Presumption
Fallacies of presumption are just that – statements that make unwarranted and often unsubstantiated assumptions. These often consist of premises based on coincidental or accidental relationships that lead to false, and sometimes superstitious, conclusions. A couple of examples:
- "Women earn less than men. Oprah Winfrey is a woman, therefore she makes less than a man."
- "The black cat ran across the path, and then the bicyclist had an accident. Therefore, black cats cause accidents."
Identifying logical fallacies is a key component of the critical thinking skills everyone, but especially children, need in order to live well and meaningfully in the world today.
Citizens who know the difference between opinions based on erroneous or false assumptions, and facts based on solid logic and reasoning skills, can make the difference between a future entrenched in fear and ignorance, or one rich in progress and social well-being.
Sources
Curtis, Gary N. "What is a Logical Fallacy?." Fallacy Files. Gary N. Curtis, 2010. Web. <http://www.fallacyfiles.org/introtof.html>.
Kemerling, Garth. "Logic." Philophy Pages. 2001. Web. <http://www.philosophypages.com>.
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