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Published online by Cambridge University Press: 24 October 2008
Toward the end of 1676 Leibniz met Spinoza a number of times. In one of those meetings Leibniz presented a proof of the possibility of God's existence. In his proof Leibniz presupposed that a proposition is necessarily true only if its truth is either demonstrable or self-evident and that the divine perfections are simple and affirmative qualities. I contend that Leibniz's presuppositions undermine, rather than establish, the necessary existence of ‘a God of the kind in whom the pious believe’. My assessment is based upon a consideration of Leibniz's argument in the context of other early papers, works written before the Discourse on Metaphysics in 1686.
1 In this essay I employ the following abbreviations: A and G: Leibniz, G. W., Philosophical Essays, edited and translated by Roger, Ariew and Daniel, Garber (Indianapolis: Hackett Publishing Company, 1989);Google Scholar G: Leibniz, G. W., Philosphische Schriften, edited by Gerhardt, C. I., 7 vols. (Berlin: Weidmann, 1875–1890);Google Scholar GM: Leibniz, G. W., Mathematische Schriften, edited by Gerhardt, C. I., 7 vols. (Berlin and Halle, 1849–1855);Google Scholar Gr: Leibniz, G. W., Textes inédits, edited by Gastron, Grua, 2 vols. (Paris: Presses Universitaires de France, 1948);Google Scholar L: Leibniz, G. W., Philosophical Papers and Letters, edited and translated by Loemker, Leroy E. (Dordrecht: D. Reidel Publishing Company, 1976);CrossRefGoogle Scholar P: Leibniz, G. W., De Summa Rerum Metaphysical Papers, 1675–1676, translated with an introduction and notes by Parkinson, G. H. R. (New Haven and London: Yale University Press, 1992);CrossRefGoogle Scholar PA: Leibniz, G. W., Samtliche Schriften und Briefe, edited by the Preussische Akademie der Wissenschaften, after 1945 the Deutsche Akadamie der Wissenschaften (Darmstadt and Leipzig: Akademie-Verlag, 1923–);Google Scholar P and M: Leibniz, G. W., Philosophical Writings, edited by Parkinson, G. H. R. and translated by Parkinson, G. H. R. and Mary, Morris (London: J. M. Dent and Sons, 1990);Google ScholarRussell, R., Bertrand, , A Critical Exposition of the Philosophy of Leibniz. With an Appendix of Leading Passages (Cambridge: C.U.P., 1900).Google Scholar
2 As Stuart Brown notes, it is generally agreed that Leibniz's ‘mature’ philosophic work began with the Discourse on Metaphysics [Leibniz (Brighton: the Harvester Press, 1984), p. 95].Google Scholar For a discussion of Leibniz's argument in light of some of his more mature philosophic commitments, see Donald Gotterbarn's paper, ‘Leibniz's Completion of Descartes's Proof,; Studia Leibnitiana, Band VII/I (1976), 105–12.Google Scholar
3 The insertion enclosed in parentheses is suggested by G. H. R. Parkinson, ‘Leibniz presumably means all other necessary propositions – i.e. those which are necessary but not indemonstrable’ (P 137). This interpretation is supported by Leibniz's remarks in ‘On Freedom and Possibility’. ‘There are two primary propositions: one, the principle of necessary things, that whatever implies a contradiction is false, and the other, the principle of contingent things, that whatever is more perfect or has more reason is true. All truths of metaphysics, or all truths that are absolutely necessary, such as those of logic, arithmetic, geometry, and the like, rest on the former principle, for someone who denies them can always be shown that the contrary implies a contradiction.’ (Gr 287/A and G 19).
4 See above, p. 38–9.
5 See above, p. 41.
6 See above, pp. 42–43.
7 William L. Rowe notes that just as one can suppose that God possesses existence as an essential property, so one could define a ‘magican’ as an essentially existing magician. But, what follows from the definition of magican is not that some actually existing entity is a magician, but that no nonexisting entity could be a magician. So, essential existence does not entail actual existence and therefore it cannot entail necessary existence. See Professor Rowe's review of Clement Dore's Theism in Faith and Philosophy, III (2) (04 1986), 205–6.Google Scholar
8 On this point see Brown's, StuartLeibniz, pp. 56–62,Google Scholar and Parkinson's, G. H. R.Logic and Reality in Leibniz's Metaphysics (Oxford: Clarendon Press, 1965), pp. 81–4.Google Scholar
9 In his discussion of Leibniz's ontological argument, G. H. R. Parkinson notes that, given Leibniz's account of divine perfections as the primitive concepts from which all complex concepts are derived, it follows that there could not be any non-compossible worlds. See Logic and Reality in Leibniz's Metaphysics, pp. 82–3.
10 For a survey of attempts made by Leibniz scholars to construct a Leibnizian account of incompatibility, see D'Agostino's, Fred paper, ‘Leibniz on Compossibility and Relational Predicates,’ in Leibniz: Metaphysics and Philosophy of Science, edited Woolhouse, R. S. (Oxford: O.U.P., 1981), pp. 89–103.Google Scholar Prior to offering his own Leibnizian explanation of incompatibility, Professor D'Agostino comments, ‘…Leibniz nowhere to my knowledge offers a completely explicit solution to this problem’ (p. 92). D'Agostino goes on to argue that an affirmation of the combinatorial operation of denial is a necessary condition for an adequate Leibnizian explanation of the incompatibility of concepts (p. 97).
11 See above, p. 43.
12 I wish to thank Keith Yandell, Mike Stevens, and Mike Schaffer for discussing various aspects of this paper with me, and Stewart Kelly for his review of the entire essay. As always, I am indebted to Mark Linville for his whimsical and insightful criticisms.