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.
To define a thing, says Dr. Watts, we must ascertain with what it agrees, then note the most remarkable attribute of difference, and join the two together.
Probity—the disposition to acknowledge the rights of mankind.
Justice—the disposition to maintain the rights of mankind.
Benevolence—the disposition to improve the rights of mankind.
Deceit—the concealed violation of the rights of mankind.
Injustice—the open violation of the rights of mankind.
Malevolence—hatred of the rights of mankind.
In defining a word we seek some class to which to refer it, that we may identify it, and fix attention upon that peculiarity by which we can distinguish it from all other things. 'Probity and 'justice' are referred to 'disposition,' with reference to the 'rights of mankind' as their sphere of existence: and acknowledgment, and maintenance, are mentioned as the distinguishing features.
Distinctions must not be made without differences. The definition should be plainer than the thing defined. Aristotle's definition of motion is considered defective in this respect:—'Motion—an act of a being in power, so far forth as it is in power.' Tautological definitions cause more to be supposed than is true—the too terse explanation leaves some necessary thing unmentioned. A perfect definition requires the union of the concise, the clear, and the adequate. Some persons are so unskilful in the analysis of terms as to occasion the advice Nil explicare—never explain yourself if you wish to be understood.
Double meanings should be avoided. The writer may himself alternate in their use, and the reader may take the word in the unintended meaning. All men have not the strong sense of Johnson. When Caleb Whiteford inquired seriously of the Doctor, whether he really considered that a man ought to be transported, like Barrington, the pickpocket, for being guilty of a double meaning. 'Sir,' said Johnson, 'if a man means well, the more he means the better'—which, whether real or fictitious, is one of the happiest answers that ever crushed a quibble.*
     * Hood's Own.
I have frequently put the question—What is consciousness? to persons who have been conscious for twenty or thirty years, but who were yet unable to reply. Had any one deprived these persons of consciousness, a judge would have hanged him for the offence; yet, could they themselves have been interrogated as to what harm they had suffered, they could not have told what they had lost. And upon the principle, that he not knowing what he has lost, is no loser, these persons, though murdered, had suffered no harm.
The various definitions of the same subject which prevail, originate in the caprice, or partial, or profound knowledge the definer may have of his subject. It seems to be admitted by logicians, that an author has a right to give whatever provisional definition he pleases of his terms. But having once given them, perspicuity requires that he should adhere to them. Any new sense in which a term is employed should be specially defined. In discoursing on an ordinary subject, as the right of public assembly,—such words as perception, conception, apprehension, might be used reciprocally, but in a dissertation on metaphysics each requires restriction in use and precision in purport.
Often genius strikes out new relations of words. In recent political debates, Mr. Cobden resorted with new force and point to a charge of rashness against ministers: he showed that rashness consisted more frequently in inaction than action. He is rash who stands surroun............