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possible worlds, and the evil that it contains affords no argument against the goodness of God.
This argument apparently satisfied the queen of Prussia. Her serfs continued to suffer the evil, while she continued to enjoy the good, and it was comforting to be assured by a great philosopher that this was just and right.
Leibniz’s solution of the problem of evil, like most of his other popular doctrines, is logically possible, but not very convincing. A Manichæan might retort that this is the worst of all possible worlds, in which the good things that exist serve only to heighten the evils. The world, he might say, was created by a wicked demiurge, who allowed free will, which is good, in order to make sure of sin, which is bad, and of which the evil outweighs the good of free will. The demiurge, he might continue, created some virtuous men, in order that they might be punished by the wicked; for the punishment of the virtuous is so great an evil that it makes the world worse than if no good men existed. I am not advocating this opinion, which I consider fantastic; I am only saying that it is no more fantastic than Leibniz’s theory. People wish to think the universe good, and will be lenient to bad arguments proving that it is so, while bad arguments proving that it is bad are closely scanned. In fact, of course, the world is partly good and partly bad, and no “problem of evil” arises unless this obvious fact is denied.
I come now to Leibniz’s esoteric philosophy, in which we find reasons for much that seems arbitrary or fantastic in his popular expositions, as well as an interpretation of his doctrines which, if it had become generally known, would have made them much less acceptable. It is a remarkable fact that he so imposed upon subsequent students of philosophy that most of the editors who published selections from the immense mass of his manuscripts preferred what supported the received interpretation of his system, and rejected as unimportant essays which prove him to have been a far more profound thinker than he wished to be thought. Most of the texts upon which we must rely for an understanding of his esoteric doctrine were first published in 1901 or 1903, in two works by Louis Couturat. One of these was even headed by Leibniz with the remark: “Here I have made enormous progress.” But in spite of this, no editor thought it worth printing until Leibniz had been dead for nearly two centuries. It is true that
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his letters to Arnauld, which contain a part of his more profound philosophy, were published in the nineteenth century; but I was the first to notice their importance. Arnauld’s reception of these letters was discouraging. He writes: “I find in these thoughts so many things which alarm me, and which almost all men, if I am not mistaken, will find so shocking, that I do not see of what use a writing can be, which apparently all the world will reject.” This hostile opinion no doubt led Leibniz, thenceforth, to adopt a policy of secrecy as to his real thoughts on philosophical subjects.
The conception of substance, which is fundamental in the philosophies of Descartes, Spinoza, and Leibniz, is derived from the logical category of subject and predicate. Some words can be either subjects or predicates; e.g., I can say “the sky is blue” and “blue is a colour.” Other words–of which proper names are the most obvious instances –can never occur as predicates, but only as subjects, or as one of the terms of a relation. Such words are held to designate substances. Substances, in addition to this logical characteristic, persist through time, unless destroyed by God’s omnipotence (which, one gathers, never happens). Every true proposition is either general, like “all men are mortal,” in which case it states that one predicate implies another, or particular, like “Socrates is mortal,” in which case the predicate is contained in the subject, and the quality denoted by the predicate is part of the notion of the substance denoted by the subject. Whatever happens to Socrates can be asserted in a sentence in which “Socrates” is the subject and the words describing the happening in question are the predicate. All these predicates put together make up the “notion” of Socrates. All belong to him necessarily, in this sense, that a substance of which they could not be truly asserted would not be Socrates, but some one else.
Leibniz was a firm believer in the importance of logic, not only in its own sphere, but as the basis of metaphysics. He did work on mathematical logic which would have been enormously important if he had published it; he would, in that case, have been the founder of mathematical logic, which would have become known a century and a half sooner than it did in fact. He abstained from publishing, because he kept on finding evidence that Aristotle’s doctrine of the syllogism was wrong on some points; respect for Aristotle made it impossible for him to believe this, so he mistakenly supposed that the errors must
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be his own. Nevertheless he cherished through his life the hope of discovering a kind of generalized mathematics, which he called Characteristica Universalis, by means of which thinking could be replaced by calculation. “If we had it,” he says, “we should be able to reason in metaphysics and morals in much the same way as in geometry and analysis.” “If controversies were to arise, there would be no more need of disputation between two philosophers than between two accountants. For it would suffice to take their pencils in their hands, to sit down to their slates, and to say to each other (with a friend as witness, if they liked): Let us calculate.”
Leibniz based his philosophy upon two logical premisses, the law of contradiction and the law of sufficient reason. Both depend upon the notion of an “analytic” proposition, which is one in which the predicate is contained in the subject–for instance, “all white men are men.” The law of contradiction states that all analytic propositions are true. The law of sufficient reason (in the esoteric system only) states that all true propositions are analytic. This applies even to what we should regard as empirical statements about matters of fact. If I make a journey, the notion of me must from all eternity have included the notion of this journey, which is a predicate of me. “We may say that the nature of an individual substance, or complete being, is to have a notion so completed that it suffices to comprehend, and to render deducible from it, all the predicates of the subject to which this notion is attributed. Thus the quality of king, which belongs to Alexander the Great, abstracting from the subject, is not sufficiently determined for an individual, and does not involve other qualities of the same subject, nor all that the notion of this prince contains, whereas God, seeing the individual notion or hecceity of Alexander, sees in it at the same time the foundation and the reason of all the predicates which can be truly attributed to him, as e.g. whether he would conquer Darius and Porus, even to knowing a priori (and not by experience) whether he died a natural death or by poison, which we can only know by history.”
One of the most definite statements of the basis of his metaphysic occurs in a letter to Arnauld:
“In consulting the notion which I have of every true proposition, I find that every predicate, necessary or contingent, past, present, or future, is comprised in the notion of the subject, and I ask no more.
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. . . The proposition in question is of great importance, and deserves to be well established, for it follows that every soul is as a world apart, independent of everything else except God; that it is not only immortal and so to speak impassible, but that it keeps in its substance traces of all that happens to it.”
He goes on to explain that substances do not act on each other, but agree through all mirroring the universe, each from its own point of view. There can be no interaction, because all that happens to each substance is part of its own notion, and eternally determined if that substance exists.
This system is evidently just as deterministic as that of Spinoza. Arnauld expresses his horror of the statement (which Leibniz had made): “That the individual notion of each person involves once for all everything that will ever happen to him.” Such a view is evidently incompatible with the Christian doctrine of sin and free will. Finding it ill received by Arnauld, Leibniz carefully refrained from. making it public.
For human beings, it is true, there is
