(2) But if this process yield no satisfactory result, make a list of the things denoted, and of those denoted by the co-ordinate and opposite words; and observe the qualities in which the things denoted agree, and in which they differ from those denoted by the contraries and opposites.  If ‘civilisation’ is to be defined, make lists of civilised peoples, of semi-civilised, of barbarous, and of savage:  now, what things are common to civilised peoples and wanting in the others respectively?  This is an exercise worth attempting.  If poetry is to be defined, survey some typical examples of what good critics recognise as poetry, and compare them with examples of bad ‘poetry,’ literary prose, oratory, and science.  Having determined the characteristics of each kind, arrange them opposite one another in parallel columns.  Whoever tries to define by this method a few important, frequently occurring words, will find his thoughts the clearer for it, and will collect by the way much information which may be more valuable than the definition itself, should he ever find one.

(3) If the genus of a word to be defined is already known, the process may be shortened.  Suppose the genus of poetry to be belles lettres (that is, ’appealing to good taste’), this suffices to mark it off from science; but since literary prose and oratory are also belles lettres, we must still seek the differentia of poetry by a comparison of it with these co-ordinate species.  A compound word often exhibits genus and difference upon its face:  as ‘re-turn,’ ‘inter-penetrate,’ ‘tuning-fork,’ ‘cricket-bat’; but the two last would hardly be understood without inspection or further description.  And however a definition be discovered, it is well to state it per genus et differentiam.

(4) In defining any term we should avoid encroaching upon the meaning of any of the co-ordinate terms; for else their usefulness is lessened:  as by making ‘law’ include ‘custom,’ or ‘wealth’ include ‘labour’ or ‘culture.’

(5) If two or more terms happen to be exactly synonymous, it may be possible (and, if so, it is a service to the language) to divert one of them to any neighbouring meaning that has no determinate expression.  Thus, Wordsworth and Coleridge took great pains to distinguish between Imagination and Fancy, which had become in common usage practically equivalent; and they sought to limit ‘imagination’ to an order of poetic effect, which (they said) had prevailed during the Elizabethan age, but had been almost lost during the Gallo-classic, and which it was their mission to restore.  Co-ordinate terms often tend to coalesce and become synonymous, or one almost supersedes the other, to the consequent impoverishment of our speech.  At present proposition (that something is the fact) has almost driven out proposal (that it is desirable to co-operate in some action).  Even good writers and speakers, by their own practice, encourage this confusion:  they submit to Parliament certain ‘propositions’ (proposals for legislation), or even make ’a proposition of marriage.’  Definition should counteract such a tendency.