Let it be supposed, that there is no other kind of causality than that according to the laws of nature. Consequently, everything that happens presupposes a previous condition, which it follows with absolute certainty, in conformity with a rule. But this previous condition must itself be something that has happened (that has arisen in time, as it did not exist before), for, if it has always been in existence, its consequence or effect would not thus originate for the first time, but would likewise have always existed. The causality, therefore, of a cause, whereby something happens, is itself a thing that has happened. Now this again presupposes, in conformity with the law of nature, a previous condition and its causality, and this another anterior to the former, and so on. If, then, everything happens solely in accordance with the laws of nature, there cannot be any real first beginning of things, but only a subaltern or comparative beginning. There cannot, therefore, be a completeness of series on the side of the causes which originate the one from the other. But the law of nature is that nothing can happen without a sufficient a priori determined cause. The proposition therefore- if all causality is possible only in accordance with the laws of nature- is, when stated in this unlimited and general manner, self-contradictory. It follows that this cannot be the only kind of causality.
From what has been said, it follows that a causality must be admitted, by means of which something happens, without its cause being determined according to necessary laws by some other cause preceding. That is to say, there must exist an absolute spontaneity of cause, which of itself originates a series of phenomena which proceeds according to natural laws- consequently transcendental freedom, without which even in the course of nature the succession of phenomena on the side of causes is never complete.