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Analytic Definition

An analytic definition tries to identify the intension of a term by providing a synonymous linguistic expression or an operational procedure for determining the applicability of the term. Of course, it isn't always easy to come up with an alternative word or phrase that has exactly the same meaning or to specify a concrete test for applicability. But when it does work, connotative definition provides an adequate means for securing the meaning of a term. Definition by Genus and Differentia Classical logicians developed an especially effective method of constructing connotative definitions for general terms, by stating their genus and differentia. The basic notion is simple: we begin by identifying a familiar, broad category or kind (the genus) to which everything our term signifies (along with things of other sorts) belongs; then we specify the distinctive features (the differentiae) that set them apart from all the other things of this kind. Consider the following definition of the word "chair" as "piece of furniture designed to be sat upon by one person at a time." In this definition, "piece of furniture" is the genus to which all chairs belong and "designed to be sat upon by one person at a time" is the differentia that distinguishes them from couches, desks, etc.

Copi and Cohen list five rules by means of which to evaluate the success of definitions by genus and differentia:

1.Focus on essential features. Although the things to which a term applies may share many distinctive properties, not all of them equally indicate its true nature. Thus, for example, a definition of "human beings" as "featherless bipeds" isn't very illuminating, even if does pick out the right individuals. A good definition tries to point out the features that are essential to the designation of things as members of the relevant group.

2.Avoid circularity. Since a circular definition uses the term being defined as part of its own definition, it can't provide any useful information; either the audience already understands the meaning of the term, or it cannot understand the explanation that includes that term. Thus, for example, there isn't much point in defining "cordless 'phone" as "a telephone that has no cord."

3.Capture the correct extension. A good definition will apply to exactly the same things as the term being defined, no more and no less. There are several ways to go wrong. Consider alternative definitions of "bird": "warm-blooded animal" is too broad, since that would include horses, dogs, and aardvarks along with birds. "feathered egg-laying animal" is too narrow, since it excludes those birds who happen to be male. and "small flying animal" is both too broad and too narrow, since it includes bats (which aren't birds) and excludes ostriches (which are). Successful intensional definitions must be satisfied by all and only those things that are included in the extension of the term they define.

4.Avoid figurative or obscure language. Since the point of a definition is to explain the meaning of a term to someone who is unfamiliar with its proper application, the use of language that doesn't help such a person learn how to apply the term is pointless. Thus, "happiness is a warm puppy" may be a lovely thought, but it is a lousy definition.

5.Be affirmative rather than negative. It is always possible in principle to explain the application of a term by identifying literally everything to which it does not apply. In a few instances, this may be the only way to go: a proper definition of the mathematical term "infinite" might well be negative, for example. But in ordinary circumstances, a good definition uses positive designations whenever it is possible to do so. Defining "honest person" as "someone who rarely lies" is a poor definition.


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