For I would fain know what substance exists, that has not something in it which manifestly baffles our understandings.

Other spirits, who see and know the nature and inward 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.