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12.6: Defining Terms- Types and Purposes of Definitions

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    9 Defining Terms: Types and Purposes of Definitions21

    Clearly defining terms is one way of helping to resolve problems of ambiguity and there are many types of definitions one can use:

    • Lexical or dictionary definitions

    The OED defines “defines” as…

    • Disambiguating definitions

    When I said…I meant…”

    • Stipulative definitions

    For the purposes of this class, a “kwijybo” is “a big dumb balding North American ape with no chin and a short temper”

    • Precising definitions

    A small amount of salt is less than .5 tsp

    • Systematic or theoretical

    Brother-in-law: husband of my sister (OR brother of my wife!)

    The point of using definitions like these is simple: to make sure that you are clear in what you say. If anything can be uncertain, it is best to define it or use other, more precise words.

    We will be covering fallacies more later in this course, but there are a few that are very relevant right now, as these are all ones that can be fixed by using a definitional approach. Again, a “fallacy” is drawing an unsupported conclusion by using a common method of reasoning that is usually in error. Being familiar with fallacies makes them very easy to recognize (and avoid yourself, as well as understand how to properly resolve them).

    Loaded Question Fallacy

    (Also known as complex question, fallacy of presupposition, trick question) The fallacy of asking a question that has a presupposition built in, which implies something (often questionable) but protects the person asking the question from accusations of false claims or even slander.

    Example: Have you stopped sleeping in unicorn sheets?

    This question is a real ‘catch-22’ since to answer ‘yes’ implies that you used to sleep in unicorn sheets but have now stopped, and to answer ‘no’ means you are still sleeping in them. The question rests on the assumption that you sleep in unicorn sheets, and so either answer to it seems to endorse that idea.


    (Also known as doublespeak) A fallacy that occurs when one uses an ambiguous term or phrase in more than one sense, thus rendering the argument misleading. The ambiguity in this fallacy is lexical and not grammatical, meaning the term or phrase that is ambiguous has two distinct meanings. In other words, it happens when one term is assumed to mean the same thing in two different contexts, but actually means two different things. One can often see equivocation in jokes.

    Example: Man is the only rational animal, and no woman is a man, so women are not rational.

    Example: If you don’t pay your exorcist you can get repossessed.

    Example: A feather is light; whatever is light cannot be dark; therefore, a feather cannot be dark.


    A fallacy of ambiguity, where the ambiguity in question arises directly from the poor grammatical structure in a sentence. The fallacy occurs when a bad argument relies on the grammatical ambiguity to sound strong and logical.

    Example: I’m going to return this car to the dealer I bought this car from. Their ad said “Used 1995 Ford Taurus with air conditioning, cruise, leather, new exhaust and chrome rims.” But the chrome rims aren’t new at all.

    There are other kinds of amphiboly fallacies, like those of ambiguous pronoun reference: “I took some pictures of the dogs at the park playing, but they were not good.” Does ‘they’ mean the dogs or the pictures “were not good”? And there is amphiboly when modifiers are misplaced, such as in a famous Groucho Marx joke: “One morning I shot an elephant in my pajamas. How he got into my pajamas I’ll never know.”

    Fallacy of the Undistributed Middle

    (Also known as undistributed middle term) A formal fallacy that occurs in a categorical syllogism (we’ll look at these later), when the middle term is undistributed is not distributed at least in one premise. According to the rules of categorical syllogism, the middle term must be distributed at least once for it to be valid.

    Example of the form: All X’s are Y’s; All Z’s are Y’s; Therefore, All X’s are Z’s.

    Example in words: All ghosts are spooky; all zombies are spooky; therefore all ghosts are


    The problem here is that you’re relating the incorrect categories with each other. It is fine to say, “All dogs are mammals, all mammals are animals, so all dogs are animals” but not “All dogs are mammals, all chihuahuas are mammals, so all chihuahuas are dogs” because even though your conclusion is true, the route that led you there is invalid.

    This page titled 12.6: Defining Terms- Types and Purposes of Definitions is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by Noah Levin (NGE Far Press) .

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