 What then can we know and with what degree of certainty? We can know that God exists with the second highest degree of assurance, that of demonstration. We also know that we exist with the highest degree of certainty. The truths of morality and mathematics we can know with certainty as well, because these are modal ideas whose adequacy is guaranteed by the fact that we make such ideas as ideal models which other things must fit, rather than trying to copy some external archetype which we can only grasp inadequately. On the other hand, our efforts to grasp the nature of external objects are limited largely to the connection between their apparent qualities. The real essence of elephants and gold is hidden from us: though in general we suppose them to be some distinct combination of atoms which cause the grouping of apparent qualities which leads us to see elephants and violets, gold and lead as distinct kinds. Our knowledge of material things is probabilistic and thus opinion rather than knowledge. Thus our “knowledge” of external objects is inferior to our knowledge of mathematics and morality, of ourselves, and of God. We do have sensitive knowledge of external objects, which is limited to things we are presently experiencing. While Locke holds that we only have knowledge of a limited number of things, he thinks we can judge the truth or falsity of many propositions in addition to those we can legitimately claim to know. This brings us to a discussion of probability.