31 / OBJECTIVE TIME RELA TIONS OF PHENOMENA. 363 left, and then to perform the same motions in the opposite direction. On the other hand, it is not left to my choice to hear the thunder either before or after I see the lightning, or to see a passing wagon now here, now there, but in these cases I am bound in the succession of my.^JQSuous repres- eptations. The possibility of interchange in the series of perceptions proves an objective coexistence, the impossi bility of this, an objective succession. But this criterion fs limited to the immediate present, and fails us when a time relation between unobserved phenomena is to be established. If I go at evening into the dining room and sec a vessel of bubbling water, which is to be used in mak- ing tea, over a burning spirit lamp, whence do I derive the knowledge that the water began, and could begin, to boil only after the alcohol had been lighted, and not before? Because I have often seen the flame precede the boiling of the water, and in this the irreversibility of the two per- ceptions has guaranteed to me the succession of the events ^rccived ? Then I may only assume that it is very probable, not that it is certain, that in this case also the order of the two events has been the same as I have observed several times before. As a matter of fact, however, we all assert that the water could not have come into a boiling condition unless the generation of heat had preceded ; that in every case tjie fire must be there before the boiling of the water can commence. Whence do we derive this must ? j Simply and alone from the thought of a causal connection Uetween the two events. Every phenomenon tnust follow in time that phenomenon of which it is the effect, and r must precede that of which it is the cause. It is through the relation of causality, and through this aMrre, that the" oBJecHv^e time'^Teiation oT phenomena is determmed. If nothing preceded an event on which it must follow accord- ing to a rule,* then all succession in perception would be / subjective merely, and nothing whatever would be objec- tively determined by it as to what was the antecedent and what the consequent in the phenomenon itself. We should then have a mere play of representations without
- " A reality following on an empty time, that is, a beginning of existence pre-
ceded by no state of things, can as little be apprehended as empty time itself." i
