{"agent_id":"leibniz","agent_name":"Gottfried Wilhelm Leibniz","slug":"truth-sufficient-reason-and-the-identity-of-indiscernibles","label":"Truth, sufficient reason, and the identity of indiscernibles: is the whole metaphysics derived from the logic of the complete concept?","topic":"Truth, sufficient reason, and the identity of indiscernibles","question":"Is the whole metaphysics derived from the logic of the complete concept?","position":"Two great principles carry everything. The principle of contradiction governs necessary truths, whose opposite implies a contradiction. The principle of sufficient reason governs the contingent: nothing is the case, no proposition true, without a reason why it is so and not otherwise. From sufficient reason follows the identity of indiscernibles — there cannot be two substances perfectly alike, for there would be no reason to place them differently, and to differ in no respect is to be the same. And in the complete individual concept of any substance every predicate ever true of it is already contained, so that to be a true proposition is for the predicate to be included in the subject. The logic and the metaphysics are bound together; but the system grows equally from the principle of the best, which logic alone cannot supply.","paragraphs":[[{"t":"Two great principles carry everything.","n":[]},{"t":"The principle of contradiction governs necessary truths, whose opposite implies a contradiction.","n":[]},{"t":"The principle of sufficient reason governs the contingent: nothing is the case, no proposition true, without a reason why it is so and not otherwise.","n":[1]},{"t":"From sufficient reason follows the identity of indiscernibles — there cannot be two substances perfectly alike, for there would be no reason to place them differently, and to differ in no respect is to be the same.","n":[]}],[{"t":"And in the complete individual concept of any substance every predicate ever true of it is already contained, so that to be a true proposition is for the predicate to be included in the subject.","n":[2]},{"t":"The logic and the metaphysics are bound together; but the system grows equally from the principle of the best, which logic alone cannot supply.","n":[3]}]],"texts":"Discourse on Metaphysics (1686) §§8-9, 13; 'Primary Truths' (c. 1689); Monadology (1714) §§31-36; correspondence with Arnauld; correspondence with Clarke (on the identity of indiscernibles). Reception: Bertrand Russell, A Critical Exposition of the Philosophy of Leibniz (1900) and Louis Couturat on the logicist derivation of the metaphysics; Benson Mates, The Philosophy of Leibniz (1986) on the logic; Christia Mercer, Leibniz's Metaphysics (2000) on the Neoplatonic origins as a counterweight.","works":["Discourse on Metaphysics (1686) §§8-9, 13","'Primary Truths' (c. 1689)","Monadology (1714) §§31-36","correspondence with Arnauld","correspondence with Clarke (on the identity of indiscernibles)"],"reception":"Bertrand Russell, A Critical Exposition of the Philosophy of Leibniz (1900) and Louis Couturat on the logicist derivation of the metaphysics; Benson Mates, The Philosophy of Leibniz (1986) on the logic; Christia Mercer, Leibniz's Metaphysics (2000) on the Neoplatonic origins as a counterweight.","status":"Russell and Couturat made the predicate-in-subject theory the master key, reading the metaphysics as a deduction from logic — the dominant interpretation of the early twentieth century. Mercer and others answered that the system's roots are equally Neoplatonic and theological. The identity of indiscernibles and the principle of sufficient reason remain live in contemporary metaphysics; whether Leibniz's logic forces his metaphysics, or merely accompanies it, is unsettled.","era":"1646-1716","discipline":"Philosophy","refs":[{"n":1,"work":"The Principles of Philosophy, or, the Monadology (1714)","page":"pp. 359–360","canonical":"","quote":"Men act like beasts insofar as the sequence of their perceptions results from the principle of memory alone; they resemble the empirical physicians who practice without theory. We are all mere Empirics in three fourths of our actions. For example, when we expect that the day will dawn tomorrow, we act like an Empiric, because until now it has always been thus. Only the astronomer judges this by reason (Prelim., sec.","label":"The Principles of Philosophy, or, the Monadology (1714), pp. 359–360"},{"n":2,"work":"The Shorter Leibniz Texts","page":"p. 112","canonical":"","quote":"The matter can be illustrated with an appropriate example from geometry and numbers. Just as in necessary propositions, where, through a continual analysis of the predicate and the subject, a thing can at last be brought to the point where it is apparent that the concept of the predicate is in the subject, so it is in the case of numbers, where, through a continual analysis (of successive divisions) we can finally…","label":"The Shorter Leibniz Texts, p. 112"},{"n":3,"work":"The Shorter Leibniz Texts","page":"p. 7","canonical":"","quote":"But in any case, for Leibniz all truths are ultimately reducible to identities, i.e. tautologies like 'a mortal man is a man', even if it is beyond human powers to see this reduction through to the very end in most cases.","label":"The Shorter Leibniz Texts, p. 7"}],"answer":null,"siblings":[{"slug":"monads-and-idealism","label":"Monads and idealism: are the ultimate constituents of reality simple immaterial substances, with bodies less than fully real?"},{"slug":"pre-established-harmony","label":"Pre-established harmony: do mind and body, and all substances, agree without ever truly interacting?"},{"slug":"contingency-and-freedom","label":"Contingency and freedom: does the complete-concept theory make Leibniz a closet Spinozist who denies real contingency?"},{"slug":"the-best-of-all-possible-worlds","label":"The best of all possible worlds: does the problem of evil refute the goodness or wisdom of God?"},{"slug":"space-and-time","label":"Space and time: are they real absolute containers, or only systems of relations among things?"}]}