| definition | The process or product of identifying a concept's referents, either 1) ostensively or 2) in the form of a proposition, and if in the latter form, then a) descriptively, or b) by means of specifying a differentia and genus in fundamental, concise terms. For related information, please see DEFINITION (OSTENSIVE), DEFINITION
(DESCRIPTIVE), DEFINITION (GENUS AND DIFFERENTIA). |
| definition (descriptive) | Definition accomplished by means of describing a thing with words, but without (yet) fully specifying a genus and differentia. For related information, please see
DEFINITION, DEFINITION (GENUS AND DIFFERENTIA),
DEFINITION (OSTENSIVE). |
| definition (genus and differentia) | Definition accomplished by means of specifying a genus and a differentia in fundamental, essential, and concise terms.1 For related information, please see DEFINITION, DEFINITION
(OSTENSIVE), DEFINITION (DESCRIPTIVE).
Elaboration By my understanding, a genus
is a wider class of things to which a particular
thing belongs. A differentia is the differentiating attribute(s) which distinguish(es) that type of thing from the wider class to which it belongs.
For example, a frog is an amphibious animal. The differentia in this case is "amphibious," and the genus is "animal."
Although this preliminary definition incorporates a differentia and a genus, and might function satisfactorily for a young child, a person might learn that there are many other amphibious animals other than frogs. Such a person might satisfy needs for deeper clarity and articulation by then formulating a more specific, genus-differentia definition.
A much more specific definition of "frog" could be: "Any of numerous tailless, aquatic, semiaquatic, or terrestrial amphibians of the order Anura and especially of the family Ranidae, characteristically having a smooth moist skin, webbed feet, and long hind legs adapted for leaping."2 In this more specific definition, broadly speaking,
the genus
is "amphibian,"
and the differentia includes all the attributes that together distinguish frogs from other amphibians.
Notes 1Although this definition and the elaboration I've provided are mine, I'm grateful for inspiration that I drew while formulating it from both Ayn Rand's nonfiction book, Introduction
to Objectivist Epistemology, and from David Kelley's book, The Art of Reasoning.
2"frog," The
American Heritage Dictionary of the English Language, 4th ed. Boston: Houghton Mifflin, 2000. www.bartleby.com/61/. [June 30, 2005.] |
| definition (ostensive) | Definition accomplished by pointing at some of a concept's specific instances.1 For related information, please see DEFINITION, DEFINITION
(DESCRIPTIVE), DEFINITION (GENUS AND DIFFERENTIA).
Elaboration
With some concepts, I've found ways to define them only ostensively.
With the concept "reality," for example, I can't define it in terms of a genus and a differentia, because there is no wider classification to which reality belongs. (In my usage in this context, "reality" means "everything that exists.") Likewise there is nothing in reality from which I could differentiate reality. The same applies to such concepts as "identity," "non-contradiction" and "causality" - as well as many others.
Notes
1Even though this is my definition, I'm grateful for the inspiration that Ayn Rand provided me with her use of similar terminology in her nonfiction book, Introduction to Objectivist Epistemology.
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