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7. Metaphysics: necessity, contingency and freedom
Central to Leibniz’s philosophy were a variety of problems concerning necessity, contingency and freedom, problems which arise in a variety of ways from a variety of sources. Spinoza stood behind many of Leibniz’s worries. According to Spinoza, everything in the world is necessary and nothing is contingent, so that things could not be other than they are. Indeed, everything that is genuinely possible is actual and if something does not actually exist, it is because it could not. Everything follows from the divine nature, not by choice but by blind necessity. Furthermore, Spinoza argued, everything in the world is determined and what we take to be human freedom is just an illusion. We think that we are free because we are ignorant of the causes outside us that determine us to do what we do.
Other problems came from Leibniz’s own views. Some came from Leibniz’s principle in accordance with which ‘when a proposition is not an identity, that is, when the predicate is not explicitly contained in the subject, it must be contained in it virtually’ (Discourse §8). If every predicate true of an individual was part of its very concept, how could it fail to be necessary? A closely related problem followed from Leibniz’s claim that every individual substance contains everything that can happen to it, past, present and future, which seems to entail that everything was determined from the beginning, and there is no room for the freedom of a creature. Here the problem concerns not necessity and contingency, but determinism and human freedom. Even if it were contingent that a certain creature has a certain built-in history, given that history, there does not appear to be room for freedom.
Leibniz offered a number of approaches to this problem in his writings. His basic response to the Spinozistic attacks on contingency is the claim that God freely chose the best of all possible worlds. He wrote in the early 1680s in an essay entitled De libertate (On freedom) ‘God produces the best not by necessity but because he wills it’ Leibniz [1680–2] 1989: 20). Yet, since God is perfect, it would seem that his nature necessarily determines his will to choose the best.
This led Leibniz directly to another account of contingency. In that same document, he continued by noting that ‘things remain possible, even if God does not choose them’. That is, even if God necessarily created the best of all possible worlds (a concession Leibniz does not always make), unactualized possibles are still, in and of themselves, possible. The recognition of such unactualized possibles is what brought him back from the precipice of necessitarianism, so Leibniz wrote in another essay from the late 1680s (Leibniz 1989: 21). Elsewhere, he characterized those possibles that God chooses to create as necessary, but only ex hypothesi, on the hypothesis that God chose to create them. Though necessary in this limited sense, they are contingent in so far as their contraries are not self-contradictory (Discourse §13).
From time to time Leibniz used the kindred notion of compossibility. Two individuals are said to be compossible when they can be actualized at the same time, and are said not to be compossible when they cannot. In this way one can say that a possible world is a maximal set of compossible individuals. The notions of compossibility and incompossibility are not, however, logical notions, taken narrowly. Two individuals may fail to fit in the same possible world because they are logically in contradiction with one another (in a sense that must be specified), or because they fail to harmonize with one another.
Leibniz sometimes also suggested that it is contingent that this particular world is the best of all possible worlds. So, even if God necessarily created the best of all possible worlds, it is still contingent that he creates this world. These arguments address the worries that derive from Spinoza’s view that God necessarily gave rise to this world (see Spinoza, B. de §4). But, as noted above, there are other more Leibnizian worries to address as well. If in any true proposition the concept of the predicate must be contained in the concept of the subject, how can any truth fail to be necessary? Leibniz gave one kind of answer in the Discourse on Metaphysics (§13) where he simply asserts that there are two kinds of conceptual containment. While all predicates are contained in the concept of the subject, some are contained necessarily, and some contingently. But in some documents, probably from the late 1680s, he attempted a different solution. He noted first that in some cases we can demonstrate that the predicate is contained in the subject in a finite number of steps. However, in other cases this cannot be done. ‘In contingent truths, even though the predicate is in the subject, this can never be demonstrated, nor can a proposition ever be reduced to an equality or to an identity, but the resolution proceeds to infinity’ (Leibniz 1989: 96). To demonstrate a contingent truth, one must show that a given individual with a given property is one among an infinity of individuals in a possible world that is the best among an infinity of other possible worlds, something that cannot be shown in a finite number of steps.
Beyond the question of necessity is the issue of human freedom. Take an individual substance, which contains everything that has happened, is happening and will happen to it. Even if one can establish that the sequence of ‘happenings’ it contains is contingent, yet by virtue of containing all these happenings, it would seem not to be free to do anything other than what it does. Contingency is thus compatible with strict determinism, which is incompatible with human freedom.
Leibniz’s solution was that while God may build certain actions into a given individual, he can build them in as free actions: ‘God sees for all time that there will be a certain Judas whose notion or idea…contains this free and future action’ (Discourse §30). God does make us with free will, and the ability to choose one thing over another. So, when he chooses to create a given individual with a given life- history, he will include the conditions that will lead that individual to choose one thing over another. But the actual choice is ours, and it is free, Leibniz argued. In this way, ‘God inclines our soul without necessitating it’ (Discourse §30). Furthermore, while we can choose other than the way we do, God in his omniscience can predict what we will actually choose, and build its consequences into our future programme. This divine foreknowledge does not change the character of the events themselves: ‘God foresees things as they are and does not change their nature.…Thus they are assured but they are not necessary’ (Dialogue effectif sur la liberté de l’homme et sur l’origine du mal (An actual dialogue on human freedom and on the origin of evil) [ 1695c] 1989: 112). Thus Leibniz had no worse problems on this score than does anyone who believes in divine omniscience.
Leibniz’s doctrine did raise a knotty problem about the identity conditions for individuals, however. If all properties of a given individual are programmed in from the beginning, then though some may be contingent, and though some may be free, still, they define the individual as the particular individual that it is; were they different, then we would be dealing with another individual altogether, it would seem. From time to time Leibniz acknowledged that we might want to talk about what might have happened if Judas (our Judas, the Judas in this possible world) had not renounced Christ (Leibniz–Arnauld Correspondence, May 1686, (Leibniz 1875–90 vol. 2: 41–2); the specific example at issue there is not Judas, as in the Discourse, but Adam). But often Leibniz seemed quite willing to embrace a different view: ‘But someone…will say, why is it that this man will assuredly commit this sin? The reply is easy: otherwise he would not be this man’ (Discourse §30). In this way, given that every substance mirrors the entire world in which it finds itself, Leibniz often committed himself to the thesis that a person can belong to only one possible world.
Garber, Daniel. Metaphysics: necessity, contingency and freedom. Leibniz, Gottfried Wilhelm (1646–1716), 1998, doi:10.4324/9780415249126-DA052-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/biographical/leibniz-gottfried-wilhelm-1646-1716/v-1/sections/metaphysics-necessity-contingency-and-freedom.
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