else. There are of course series of motives, since the resolve to attain an end becomes the motive for the resolve to use a whole series of means ; still this series invariably ends a parte priori in a representation belonging to one of our two first classes, in which lies the motive which originally had the power to set this individual will in motion. The fact that it was able to do this, is a datum for knowing the empirical character here given, but it is impossible to answer the question why that particular motive acts upon that particular character; because the intelligible character lies outside Time and never becomes an Object. Therefore the series of motives, as such, finds its termination in some such final motive and, according to the nature of its last link, passes into the series of causes, or that of reasons of knowledge: that is to say, into the former, when that last link is a real object ; into the latter, when it is a mere conception.
§ 51. Each Science has for its Guiding Thread one of the Forms of the Principle of Sufficient Reason in preference to the others.
As the question why always demands a sufficient reason, and as it is the connection of its notions according to the principle of sufficient reason which distinguishes science from a mere aggregate of notions, we have called that why the parent of all science (§ 4). In each science, moreover, we find one of the forms of that principle predominating over the others as its guiding-thread. Thus in pure Mathematics the reason of being is the chief guiding-thread (although the exposition of the proofs proceeds according to the reason of knowing only); in applied Mathematics the law of causality appears together with it, but in Physics, Chemistry, Geology, &c., that law entirely predominates. The principle of sufficient
