same essence.  In the first of these, the mind, in making its complex ideas of substances, only follows nature; and puts none together which are not supposed to have a union in nature.  Nobody joins the voice of a sheep with the shape of a horse; nor the colour of lead with the weight and fixedness of gold, to be the complex ideas of any real substances; unless he has a mind to fill his head with chimeras, and his discourse with unintelligible words.  Men observing certain qualities always joined and existing together, therein copied nature; and of ideas so united made their complex ones of substances.  For, though men may make what complex ideas they please, and give what names to them they will; yet, if they will be understood when they speak of things really existing, they must in some degree conform their ideas to the things they would speak of; or else men’s language will be like that of Babel; and every man’s words, being intelligible only to himself, would no longer serve to conversation and the ordinary affairs of life, if the ideas they stand for be not some way answering the common appearances and agreement of substances as they really exist.

29.  Our Nominal Essences of substances usually consist of a few obvious qualities observed in things.

Secondly, Though the mind of man, in making its complex ideas of substances, never puts any together that do not really, or are not supposed to, co-exist; and so it truly borrows that union from nature:  yet the number it combines depends upon the various care, industry, or fancy of him that makes it.  Men generally content themselves with some few sensible obvious qualities; and often, if not always, leave out others as material and as firmly united as those that they take.  Of sensible substances there are two sorts:  one of organized bodies, which are propagated by seed; and in these the shape is that which to us is the leading quality, and most characteristical part, that determines the species.  And therefore in vegetables and animals, an extended solid substance of such a certain figure usually serves the turn.  For however some men seem to prize their definition of animal rationale, yet should there a creature be found that had language and reason, but partaked not of the usual shape of a man, I believe it would hardly pass for a man, how much soever it were animal rationale.  And if Balaam’s ass had all his life discoursed as rationally as he did once with his master, I doubt yet whether any one would have thought him worthy the name man, or allowed him to be of the same species with himself.  As in vegetables and animals it is the shape, so in most other bodies, not propagated by seed, it is the colour we most fix on, and are most led by.  Thus where we find the colour of gold, we are apt to imagine all the other qualities comprehended in our complex idea to be there also:  and we commonly take these two obvious qualities, viz. shape and colour, for so presumptive ideas of several species, that in a good picture, we readily say, this is a lion, and that a rose; this is a gold, and that a silver goblet, only by the different figures and colours represented to the eye by the pencil.