DEFINITION is the explanation or statement of the meaning of a word, viz., either the meaning it usually bears, or that which the speaker or writer, for the particular purposes of his discourse, intends to annex to it. To give merely another synonymous name—to say, for instance, that " man is a human being"—is not commonly considered a definition at all. Names requiring definition mostly imply, or connote, a set of attributes. To define such a name, then, is to enumerate all the attributes connoted by it. Hence, definition is a kind of analysis. If we were to define " man " as " a rationat animal," the definition would be imperfect; for no one would call such beings as Swift's Ilouyhnhms men, which shows that, in the common acceptation of the word man, it connotes among other things a certain form. Definition, then, is of the nature of essential propositions; it conveys no information about the object to any one who is aware of the connotation of its name; it is only a statement of all the attributes, the absence of any one of which would make the object cease to be called by that name.
The definition, "Man is a rational animal," though incomplete, is correct so far as it goes; though it does not enumerate all the essential attributes—i.e., all the attri 17utes connoted by the name man, yet those it does enumerate are connoted by the name, and are sufficient to mark out its denotation—that is, to distinguish all the beings known to exist to whom it can properly be applied. Such is generally held, therefore, to be a complete definition, though logically imperfect; but to say that "Mau is a featherless biped," involves a different kind of imperfection. The attribute featherless, though actually tine of all men, and therefore serving to distinguish them from the only other bipeds, the birds, is no part of the meaning of the word, but is what logi cians call an accidental attribute. This kind of imperfect definition is called a descrip tion. Such definitions are very common in science, and serve special purposes of classi fication. In Ouvier's Animal Kingdom, man is defined or described as " a mamin Herons animal having two hands." A distinction is generally drawn between definitions of names and definitions of things, or nominal and real definitions. A real definition is intended, it is said, to explain and unfold the nature of the thing." In objection to this view, it is replied, that no definition can unfold the whole nature of a thing, and every true proposition respecting it unfolds some part of its nature: of all the propositions, then, unfolding its nature, how shall we distinguish those that define it from the others? This ques tion has never been answered. The fact seems to be that "all definitions are definitions
of names, and of names only," but that many expressions that pass for definitions, are something more. They not only define the name of the thing, but they comprise a tacit assumption. that a thing with such attributes does or may exist. This is the case with the definitions of geometry; and it is from these tacit postulates that the consequences are deduced, and not from the mere definition of the meaning of a word.
As there can be no accurate diScuSsiOn unless all the terms employed have a distinct meaning recognized by all parties, it is often necessary to have recourse to formal defi nitions of important names. One of the most effectual devices ever yet discovered for settling the signification of terms, is to declare the meaning opposed to what is intended; in this way any ambiguity in the language is at once done away with. Thus, the word " natural " conveys no clear meaning of itself; but if we state what we mean to exclude when we use it, we narrow the variety of significations to some one. We may oppose it to "moral," and then it means something connected with the world of mat ter; we may oppose it to "constrained" or compelled, giving it the meaning of spon taneous or free; other contrasts are the "artificial," the "distorted," in copying or representing things, etc.
The scholastic logicians made definition consist in stating, first, the "genus" that a thing belonged to, and secondly, the "difference" or peculiarities that separate it from all tlie other members of the same genus. This suits for natural history, and for all subjects analogous thereto. For example, if we were attemptiug to define " poetry," we could not do better than proceed per genus et differentiam. Poetry belongs to the class of fine arts: it has all the characters common to painting, sculpture, architecture, music, etc. Consequently, if we are well acquainted with these other subjects, we can draw from them part of the characteristics that belong to poetry; for example, its hav ing for its end refined pleasure. We then inquire into the difference between it and the others, which we find to be the use of a peculiar medium or instrumentality—viz., thoughts expressed in language. If we would give a more particular account of the meaning, we should find it necessary to specify the kinds of poetry, or to find out the differences of epic, dramatic, lyric, etc.; which would be to define, not the subject itself, but its subordinate species. See J. S. 31111's Logic, vol. i. 182.