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The ontological argument depends upon the distinction between existence and essence. Any ordinary person or thing, it is held, on the one hand exists, and on the other hand has certain qualities, which make up his or its “essence.” Hamlet, though he does not exist, has a certain essence: he is melancholy, undecided, witty, etc. When we describe a person, the question whether he is real or imaginary remains open, however minute our description may be. This is expressed in scholastic language by saying that, in the case of any finite substance, its essence does not imply its existence. But in the case of God, defined as the most perfect Being, Saint Anselm, followed by Descartes, maintains that essence does imply existence, on the ground that a Being who possesses all other perfections is better if He exists than if He does not, from which it follows that if He does not He is not the best possible Being.
Leibniz neither wholly accepts nor wholly rejects this argument; it needs to be supplemented, so he says, by a proof that God, so defined, is possible. He wrote out a proof that the idea of God is possible, which he showed to Spinoza when he saw him at the Hague. This proof defines God as the most perfect Being, i.e., as the subject of all perfections, and a perfection is defined as a “simple quality which is positive and absolute, and expresses without any limits whatever it does express.” Leibniz easily proves that no two perfections, as above defined, can be incompatible. He concludes: “There is, therefore, or there can be conceived, a subject of all perfections, or most perfect Being. Whence it follows also that He exists, for existence is among the number of the perfections.”
Kant countered this argument by maintaining that “existence” is not a predicate. Another kind of refutation results from my theory of descriptions. The argument does not, to a modern mind, seem very convincing, but it is easier to feel convinced that it must be fallacious than it is to find out precisely where the fallacy lies.
The cosmological argument is more plausible than the ontological argument. It is a form of the First-Cause argument, which is itself derived from Aristotle’s argument of the unmoved mover. The FirstCause argument is simple. It points out that everything finite has a cause, which in turn had a cause, and so on. This series of previous causes cannot, it is maintained, be infinite, and the first term in the series must itself be uncaused, since otherwise it would not be the first
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term. There is therefore an uncaused cause of everything, and this is obviously God.
In Leibniz the argument takes a somewhat different form. He argues that every particular thing in the world is “contingent,” that is to say, it would be logically possible for it not to exist; and this is true, not only of each particular thing, but of the whole universe. Even if we suppose the universe to have always existed, there is nothing within the universe to show why it exists. But everything has to have a sufficient reason, according to Leibniz’s philosophy; therefore the universe as a whole must have a sufficient reason, which must be outside the universe. This sufficient reason is God.
This argument is better than the straightforward First-Cause argument, and cannot be so easily refuted. The First-Cause argument rests on the assumption that every series must have a first term, which is false; for example, the series of proper fractions has no first term. But Leibniz’s argument does not depend upon the view that the universe must have had a beginning in time. The argument is valid so long as we grant Leibniz’s principle of sufficient reason, but if this principle is denied it collapses. What exactly Leibniz meant by the principle of sufficient reason is a controversial question. Couturat maintains that it means that every true proposition is “analytic,” i.e., such that its contradictory is self-contradictory. But this interpretation (which has support in writings that Leibniz did not publish) belongs, if true, to the esoteric doctrine. In his published works he maintains that there is a difference between necessary and contingent propositions, that only the former follow from the laws of logic, and that all propositions asserting existence are contingent, with the sole exception of the existence of God. Though God exists necessarily, He was not compelled by logic to create the world; on the contrary, this was a free choice, motivated, but not necessitated, by His goodness.
It is clear that Kant is right in saying that this argument depends upon the ontological argument. If the existence of the world can only be accounted for by the existence of a necessary Being, then there must be a Being whose essence involves existence, for that is what is meant by a necessary Being. But if it is possible that there should be a Being whose essence involves existence, then reason alone, without experience, can define such a Being, whose existence will follow from the ontological argument; for everything that has to do only with
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essence can be known independently of experience–such at least is Leibniz’s view. The apparent greater plausibility of the cosmological as opposed to the ontological argument is therefore deceptive.
The argument from the eternal truths is a little difficult to state precisely. Perhaps we shall do well to state it first in rough outline, and only then proceed to the complete picture. Roughly, the argument is this: Such a statement as “it is raining” is sometimes true and sometimes false, but “two and two are four” is always true. All statements that have only to do with essence, not with existence, are either always true or never true. Those that are always true are called “eternal truths.” The gist of the argument is that truths are part of the contents of minds, and that an eternal truth must be part of the content of an eternal mind. There is already an argument not unlike this in Plato, where he deduces immortality from the eternity of the ideas. But in Leibniz the argument is more developed. He holds that the ultimate reason for contingent truths must be found in necessary truths. The argument here is as in the cosmological argument: there must be a reason for the whole contingent world, and this reason cannot itself be contingent, but must be sought among eternal truths. But a reason for what exists must itself exist; therefore eternal truths must, in some sense, exist, and they can only exist as thoughts in the mind of God. This argument is really only another form of the cosmological argument. It is, however, open to the further objection that a truth can hardly be said to “exist” in a mind which apprehends it.
The argument from the pre-established harmony, as Leibniz states it, is only valid for those who accept his windowless monads which all mirror the universe. The argument is that, since all the clocks keep time with each other without any causal interaction, there must have been a single outside Cause that regulated all of them. The difficulty, of course, is the one that besets the whole monadology: if the monads never interact, how does any one of them know that there are any others? What seems like mirroring the universe may be merely a dream. In fact, if Leibniz is right, it is merely a dream, but he has ascertained somehow that all the monads have similar dreams at the same time. This, of course, is fantastic, and would never have seemed credible but for the previous history of Cartesianism.
Leibniz’s argument, however, can be freed from dependence on his peculiar metaphysic, and transformed into what is called the argu-
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ment from design. This argument contends that, on a survey of the known world, we find things which cannot plausibly be explained as the product of blind natural forces, but are much more reasonably to be regarded as evidences of a beneficent purpose.
This argument has no formal logical defect; its premisses are empirical, and its conclusion professes to be reached in accordance with the usual canons of empirical inference. The question whether it is to be accepted or not turns, therefore, not on general metaphysical questions, but on comparatively detailed considerations. There is one important difference between this argument and the others, namely, that the God whom (if valid) it demonstrates need not have all the usual metaphysical attributes. He need not be omnipotent or omniscient; He may be only vastly wiser and more powerful than we are. The evils in the world may be due to His limited power. Some modern theologians have made use of these possibilities in forming their conception of God. But such speculations are remote from the philosophy of Leibniz, to which we must now return.
One of the most characteristic features of that philosophy is the doctrine of many possible worlds. A world is “possible” if it does not contradict the laws of logic. There are an infinite number of possible worlds, all of which God contemplated before creating the actual world. Being good, God decided to create the best of the possible worlds, and He considered that one to be the best which had the greatest excess of good over evil. He could have created a world containing no evil, but it would not have been so good as the actual world. That is because some great goods are logically bound up with certain evils. To take a trivial illustration, a drink of cold water when you are very thirsty on
