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. For in all these and the like qualities, one has as good a right to be put into the complex idea
of that substance wherein they are all joined as another. And therefore different men, leaving out or putting in
several simple ideas which others do not, according to their various examination, skill, or observation of that
subject, have different essences of gold, which must therefore be of their own and not of nature's making.
