We may take as an example our perception of things in space. How much of what we see is given in present sense-perception? This is a question to which there is no definite answer. We do not know what the presentations of vision were like before we had learnt to see as a fully conscious human being sees. We have no right to assume, that after we have learned to see in this way the actual sense-presentation remains the same as it was in a different stage of our visual education. We can give no precise meaning in the way of a time-limit to the _presentness_ of perception. But we know this much, that it takes a long time and many kinds of experience to learn to see as an educated human being sees, and that this acquired capacity is never at a stand-still, but is always being extended or diminished according to the vitality, growth, or atrophy of our apperceptive masses. There is always a certain element of amplification or interpretation, which by experience, or attentive introspection we can eliminate from the data, apparently forced upon us by reality, although these data themselves are modified through and through both by habitual interpretation, and by the very defining attention which aims at eliminating all amplification from them. But yet the whole of sense-perception has a peculiar quality in being _present_. Artificial though it is, it yet, relatively speaking, contains an irreducible datum. It is distinguishable from everything which is not present. It is pervaded by something which we cannot reduce to {29} intellectual relation, though if we withdrew from it all that is relation, the apparent datum would be gone. Now Knowledge is the affirmation or judgment which identifies the constructive interpretation of our present perception with the reality which present perception forces upon us. This is clear enough to begin with, but will have to be modified below to suit the more circuitous or mediate types of Judgment. I take two examples, one from sight and one from sound.