14.  In Simple Ideas, either by synonymous terms, or by showing examples.

I. First, when a man makes use of the name of any simple idea, which he perceives is not understood, or is in danger to be mistaken, he is obliged, by the laws of ingenuity and the end of speech, to declare his meaning, and make known what idea he makes it stand for.  This, as has been shown, cannot be done by definition:  and therefore, when a synonymous word fails to do it, there is but one of these ways left.  First, Sometimes the naming the subject wherein that simple idea is to be found, will make its name to be understood by those who are acquainted with that subject, and know it by that name.  So to make a countryman understand what FEUILLEMORTE colour signifies, it may suffice to tell him, it is the colour of withered leaves falling in autumn.  Secondly, but the only sure way of making known the signification of the name of any simple idea, is by presenting to his senses that subject which may produce it in his mind, and make him actually have the idea that word stands for.

15.  In mixed Modes, by Definition.

II.  Secondly, Mixed modes, especially those belonging to morality, being most of them such combinations of ideas as the mind puts together of its own choice, and whereof there are not always standing patterns to be found existing, the signification of their names cannot be made known, as those of simple ideas, by any showing:  but, in recompense thereof, may be perfectly and exactly defined.  For they being combinations of several ideas that the mind of man has arbitrarily put together, without reference to any archetypes, men may, if they please, exactly know the ideas that go to each composition, and so both use these words in a certain and undoubted signification, and perfectly declare, when there is occasion, what they stand for.  This, if well considered, would lay great blame on those who make not their discourses about moral things very clear and distinct.  For since the precise signification of the names of mixed modes, or, which is all one, the real essence of each species is to be known, they being not of nature’s, but man’s making, it is a great negligence and perverseness to discourse of moral things with uncertainty and obscurity; which is more pardonable in treating of natural substances, where doubtful terms are hardly to be avoided, for a quite contrary reason, as we shall see by and by.

16.  Morality capable of Demonstration.