But yet so far as any complex idea of any sort of substances contains in it any simple idea, whose NECESSARY co-existence with any other MAY be discovered, so far universal propositions may with certainty be made concerning it: v.g.
could any one discover a necessary connexion between malleableness and the colour or weight of gold, or any other part of the complex idea signified by that name, he might make a certain universal proposition concerning gold in this respect; and the real truth of this proposition, that ALL GOLD IS MALLIABLE, would be as certain as of this, THE THREE ANGLES OF ALL RIGHT-LINED TRIANGLES ARE ALL EQUAL TO TWO RIGHT ONES.
11.

The Qualities which make our complex Ideas of Substances depend mostly on external, remote, and unperceived Causes.
Had we such ideas of substances as to know what real constitutions produce those sensible qualities we find in them, and how those qualities flowed from thence, we could, by the specific ideas of their real essences in our own minds, more certainly find out their properties, and discover what qualities they had or had not, than we can now by our senses: and to know the properties of gold, it would be no more necessary that gold should exist, and that we should make experiments upon it, than it is necessary for the knowing the properties of a triangle, that a triangle should exist in any matter, the idea in our minds would serve for the one as well as the other.

But we are so far from being admitted into the secrets of nature, that we scarce so much as ever approach the first entrance towards them.

For we are wont to consider the substances we meet with, each of them, as an entire thing by itself, having all its qualities in itself, and independent of other things; overlooking, for the most part, the operations of those invisible fluids they are encompassed with, and upon whose motions and operations depend the greatest part of those qualities which are taken notice of in them, and are made by us the inherent marks of distinction whereby we know and denominate them.

Put a piece of gold anywhere by itself, separate from the reach and influence of all other bodies, it will immediately lose all its colour and weight, and perhaps malleableness too; which, for aught I know, would be changed into a perfect friability.