"Experience," as they use the term, consists in sensations and their association,--"consecution" as Leibniz calls it. Experience is the stage of knowledge reached by animals, and in which the majority of men remain,--and indeed all men in the greater part of their knowledge. Leibniz takes just the same position regarding the larger part of our knowledge which Hume takes regarding it all. It consists simply in associations of such a nature that when one part recurs there is a tendency to expect the recurrence of the other member. It resembles reason, but it is based on the accidental experience of events in a consecutive order, and not on knowledge of their causal connection. We all expect the sun to rise to-morrow; but with all of us, excepting the astronomer, such expectation is purely "empirical," being based on the images of past experiences which recur. The astronomer, however, sees into the grounds, that is, the reasons, of the expectation, and hence his knowledge is rational. Thus we have two grades of knowledge,--one empirical, consisting of knowledge of facts; the other rational, being of the truths of reason. The former is contingent and particular, the latter is necessary and universal. Leibniz insists, with a pertinacity which reminds us of Kant, that "experience" can give instances or examples only, and that the fact that anything has happened in a given way any number of times in the past, can give no assurance that it will continue to do so in the future. There is nothing in the nature of the case which renders its exact opposite impossible. But a rational truth is necessary, for its opposite is impossible, being irrational or meaningless. This may not always be evident in the case of a complex rational truth; but if it be analyzed into simpler elements, as a geometrical proposition into definitions, axioms, and postulates, the absurdity of its opposite becomes evident. Sensation, in conclusion, is the having of confused ideas,--ideas corresponding to matter. Experience is the association of these confused ideas, and their association according to their accidental juxtaposition in the life of the soul. It therefore is not only thoroughly sensible, but is also phenomenal. Its content is sensations; its form is contingent and particular consecution. Both form and content, accordingly, need to be reconstructed if they are to be worthy of the name of science or of knowledge. This is the position which Leibniz assumes as against the empiricist, Locke. The details of this reconstruction, its method and result, we must leave till we come in the course of the argument again to the subject of knowledge. CHAPTER VI. THE IMPULSES AND THE WILL.