Grant that either the world itself is necessary, or that there is contained in it a necessary existence. Two cases are possible. First, there must either be in the series of cosmical changes a beginning, which is unconditionally necessary, and therefore uncaused- which is at variance with the dynamical law of the determination of all phenomena in time; or, secondly, the series itself is without beginning, and, although contingent and conditioned in all its parts, is nevertheless absolutely necessary and unconditioned as a whole- which is self-contradictory. For the existence of an aggregate cannot be necessary, if no single part of it possesses necessary existence.
Grant, on the other band, that an absolutely necessary cause exists out of and apart from the world. This cause, as the highest member in the series of the causes of cosmical changes, must originate or begin* the existence of the latter and their series. In this case it must also begin to act, and its causality would therefore belong to time, and consequently to the sum total of phenomena, that is, to the world. It follows that the cause cannot be out of the world; which is contradictory to the hypothesis. Therefore, neither in the world, nor out of it (but in causal connection with it), does there exist any absolutely necessary being.
*The word begin is taken in two senses. The first is active- the cause being regarded as beginning a series of conditions as its effect (infit). The second is passive- the causality in the cause itself beginning to operate (fit). I reason here from the first to the second.