 Leibniz’s demonstration is slightly informal here (as one might expect in a dialogue), but it could easily be reconstructed in deductive form. In 1675–6 Leibniz wrote a number of unpublished papers and notes on metaphysical topics (most of the papers are included in Parkinson’s De Summa Rerum: Metaphysical Papers, 1675–1676).  These texts include definitions of key metaphysical concepts and many informal demonstrations of metaphysical propositions. In the late 1670s Leibniz completed several short drafts of works that were divided into axioms, definitions, and propositions, although the subject matter of those works was not strictly metaphysical (see De Obligatione Credendi A VI.iv.c.2149–2155 and Animadversiones in schedam ex Batavis Missam A VI.iv.c.2204–2210). In 1679 Leibniz quickly composed a work that was closer to the ideal of a demonstrative science of metaphysics than anything he had written to date (De Affectibus AVI.iv.b.1410–1441). It contained a long list of definitions of key terms along with some demonstrations of metaphysical principles and theses. Leibniz’s project continued in the 1680s in a series of extensive definitional studies of key concepts (see, e.g., De Notionibus Omnia Quae Cogitamus Continentibus A.VI.iv.a.398–405, Definitiones Notionum Metaphysicarum atque Logicarum A.VI.iv.a.624–630, and Tabula Notionum Praeparanda A.VI.iv.a.630–635). By 1690 Leibniz had developed a logical calculus for expressing identity and inclusion relations among concepts. Around this time, however, Leibniz began to doubt whether it was possible to discover absolutely primitive concepts. He also did not succeed in developing his purely formal system of representation, the universal characteristic. Without primitive concepts or the universal characteristic it was not possible for Leibniz to attain his ideal of a fully demonstrative metaphysics. It is plausible to think that Leibniz could nevertheless have completed a work that was an approximation of the ideal, written in Latin and using non-primitive concepts. Leibniz insisted throughout his later years that he could complete a work along these lines. In 1710, for example, he explains to correspondent Charles Hugony that in his (Leibniz’s) recently published Essais de théodicée he set forth one part of his views “in an informal manner” and that he is “thinking of [writing] a Latin work in which I will try to unfold my entire system” (G 3:680). And in 1715 Leibniz writes to Biber: