For we, having need of general names for present use, stay not for a perfect discovery of all those qualities which would BEST show us their most material differences and agreements; but we ourselves divide them, by certain obvious appearances, into species, that we may the easier under general names communicate our thoughts about them.

For, having no other knowledge of any substance but of the simple ideas that are united in it; and observing several particular things to agree with others in several of those simple ideas; we make that collection our specific idea, and give it a general name; that in recording our thoughts, and in our discourse with others, we may in one short word designate all the individuals that agree in that complex idea, without enumerating the simple ideas that make it up; and so not waste our time and breath in tedious descriptions: which we see they are fain to do who would discourse of any new sort of things they have not yet a name for.
31.

Essences of Species under the same Name very different in different minds.
But however these species of substances pass well enough in ordinary conversation, it is plain that this complex idea wherein they observe several individuals to agree, is by different men made very differently; by some more, and others less accurately.

In some, this complex idea contains a greater, and in others a smaller number of qualities; and so is apparently such as the mind makes it.

The yellow shining colour makes gold to children; others add weight, malleableness, and fusibility; and others yet other qualities, which they find joined with that yellow colour, as constantly as its weight and fusibility.