constitution of things, how much must they exceed us in knowledge?  To which, if we add larger comprehension, which enables them at one glance to see the connexion and agreement of very many ideas, and readily supplies to them the intermediate proofs, which we by single and slow steps, and long poring in the dark, hardly at last find out, and are often ready to forget one before we have hunted out another; we may guess at some part of the happiness of superior ranks of spirits, who have a quicker and more penetrating sight, as well as a larger field of knowledge.]

But to return to the argument in hand:  our knowledge, I say, is not only limited to the paucity and imperfections of the ideas we have, and which we employ it about, but even comes short of that too:  but how far it reaches, let us now inquire.

7.  How far our Knowledge reaches.

The affirmations or negations we make concerning the ideas we have, may, as I have before intimated in general, be reduced to these four sorts, viz. identity, co-existence, relation, and real existence.  I shall examine how far our knowledge extends in each of these: 

8.  Firstly, Our Knowledge of Identity and Diversity in ideas extends as far as our Ideas themselves.

First, as to identity and diversity.  In this way of agreement or disagreement of our ideas, our intuitive knowledge is as far extended as our ideas themselves:  and there can be no idea in the mind, which it does not, presently, by an intuitive knowledge, perceive to be what it is, and to be different from any other.

9.  Secondly, Of their Co-existence, extends only a very little way.

Secondly, as to the second sort, which is the agreement or disagreement of our ideas in co-existence, in this our knowledge is very short; though in this consists the greatest and most material part of our knowledge concerning substances.  For our ideas of the species of substances being, as I have showed, nothing but certain collections of simple ideas united in one subject, and so co-existing together; v.g. our idea of flame is a body hot, luminous, and moving upward; of gold, a body heavy to a certain degree, yellow, malleable, and fusible:  for these, or some such complex ideas as these, in men’s minds, do these two names of the different substances, flame and gold, stand for.  When we would know anything further concerning these, or any other sort of substances, what do we inquire, but what other qualities or powers these substances have or have not?  Which is nothing else but to know what other simple ideas do, or do not co-exist with those that make up that complex idea?

10.  Because the Connexion between simple Ideas in substances is for the most part unknown.

This, how weighty and considerable a part soever of human science, is yet very narrow, and scarce any at all.  The reason whereof is, that the simple ideas whereof our complex ideas of substances are made up are, for the most part, such as carry with them, in their own nature, no visible necessary connexion or inconsistency with any other simple ideas, whose co-existence with them we would inform ourselves about.