No difficulty is unsurmountable, if words be allowed to pass
without meaning.—Lord Kames.
As every proposition consists of two names, and as every proposition affirms or denies one of these names of the other, the value of definition, which fixes the import of names, is apparent.
'A name is a word taken at pleasure to serve for a mark, which may raise in our mind a thought like to some thought we had before, and which being pronounced to others, may be to them a sign of what thought the speaker had before in his mind [Hobbes]. This simple definition of a name, as a word (or set of words) serving the double purpose of a mark to recall to ourselves the likeness of a former thought, and a sign to make it known to others, appears unexceptionable.'*
Definition originates in accurate and comprehensive observation. 'There cannot be,' says Mill, 'agreement about the definition of a thing, until there is agreement about the thing itself. To define a thing is to select from among the whole of its properties those which shall be understood to be designated and declared by its name; and the properties must be very well known to us before we can be competent to determine which of them are fittest to be chosen for this purpose.'**
'The simplest and most correct notion of a definition is, a proposition declaratory of the meaning of a word; namely, either the meaning which it bears in common acceptation, or that which the speaker or writer, for the particular purposes of his discourse, intends to annex to it.'***
* J. Stuart Mill: System of Logic, 2nd ed., chap. 11, sec.
I. p. 27.
** Introduction to Logic, p. 1.
*** Mill's Logic, p. 183, vol. 1.
But with most persons the object of a definition is merely to guide them to the correct use of a term as a protection against applying it in a manner inconsistent with custom and convention. Anything, therefore, is to them a sufficient definition of a term which will serve as a correct index to what the term denotes; although not embracing the whole, and sometimes perhaps not even any part of what it connotes.
Definitions are sometimes explained as being of two kinds—of things and words.
The definition of words is the explanation of the sense in which they are used.
The definition of things is an explanation of the specific properties by which they differ from all other things.