and in this the irreversibility of the two perceptions has guaranteed to me the succession of the events perceived?  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 the fire must be there before the boiling of the water can commence.  Whence do we derive this must?  Simply and alone from the thought of a causal connection between the two events.  Every phenomenon must follow in time that phenomenon of which it is the effect, and must precede that of which it is the cause.  It is through the relation of causality, and through this alone, that the objective time relation of phenomena is determined.  If nothing preceded an event on which it must follow according to a rule,[1] then all succession in perception would be subjective merely, and nothing whatever would be objectively 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 significance for the real succession of events.  Only the thought of a rule, according to which the antecedent state contains the necessary condition of the consequent state, justifies us in transferring the time order of our representations to phenomena.[2] Nay, even the distinction between the phenomenon itself, as the object of our representations, and our representations of it, is effected only by subjecting the phenomenon to this rule, which assigns to it its definite position in time after another phenomenon by which it is caused, and thus forbids the inversion of the perceptions.  We can derive the rule of the understanding which produces the objective time order of the manifold from experience, only because we have put it into experience, and have first brought experience into being by means of the rule.  We recapitulate in Kant’s own words:  The objective (time) relation of phenomena remains undetermined by mere perception (the mere succession in my apprehension, if it is not determined by means of a rule in relation to an antecedent, does not guarantee any succession in the object).  In order that this may be known as determined, the relation between the two states must be so conceived (through the understanding’s concept of causality) that it is thereby determined with necessity which of them must be taken as coming first, and which second, and not conversely.  Thus it is only by subjecting the succession of phenomena to the law of causality that empirical knowledge of them is possible.  Without the concept of cause no objective time determination, and hence, without it, no experience.

[Footnote 1:  “A reality following on an empty time, that is, a beginning of existence preceded by no state of things, can as little be apprehended as empty time itself.”]