On the ultimate origin of things, 1697 (1890). (G. M. Duncan, Trans.). In G[e.] W. Leibnitz & G. M. Duncan (Trans.), The philosophical works of Leibnitz, comprising the monadology, new system of nature, principles of nature and of grace, letters to Clarke, refutation of Spinoza, and his other important philosophical opuscules, together with the abridgment of the theodicy and extracts form the new essays on human understanding (pp. 100-106). New Haven, CT, US: Tuttle, Morehouse & Taylor.
http://dx.doi.org/10.1037/12983-017
The reasons of the world, therefore, lie hidden in something extra-mundane different from the chain of states or series of things, the aggregate of which constitutes the world. We must therefore pass from physical or hypothetical necessity, which determines the posterior states of the world by the prior, to something which is absolute or metaphysical necessity, the reason for which cannot be given. For the present world is necessary, physically or hypothetically, but not absolutely or metaphysically. It being granted, indeed, that the world is such as it is, it follows that things may hereafter be such as they are. But as the ultimate origin must be in something which is metaphysically necessary, and as the reason of the existing can only be from the existing, there must exist some one being metaphysically necessary, or whose essence is existence; and thus there exists something which differs from the plurality of beings or from the world, which, as we have recognized and shown, is not metaphysically necessary. (PsycINFO Database Record (c) 2016 APA, all rights reserved)