Few philosophical theses are so renowned as Leibniz's illustrious claim that this is the best of all possible worlds. Ironically, the doctrine's great fame is due more to the ridicule it received in Candide than to broad public familiarity with Leibniz's ideas. Even among philosophers well acquainted with Leibnizian texts, the subject of God's standards of perfection has only recently begun to receive detailed discussion. Yet these standards are essential to the meaning of the best possible world doctrine, and the place of humanity in the divine scheme is at the heart of Leibniz's treatment of the problem of evil. Consequently, it behooves us to ask what canons God invokes when he compares possible worlds, and in what ways these standards affect the prospects for human well-being.

The Discourse on Metaphysics of 1686 is generally regarded as the first complete presentation of Leibniz's mature metaphysics. In this chapter, we trace the development of that philosophy from Leibniz's youth, through his years in Paris, to his time in Hanover. Because the metaphysics of the 1680s has lately received so much attention and because the importance of the earlier philosophy has generally not been recognized, we concentrate on Leibniz's thought prior to 1680. In section I, we present the intellectual context in which his youthful metaphysics is most easily understood and summarize both his original metaphysical principles and his first conception of substance. We claim that these metaphysical principles, all of which concern substance, form the bedrock of Leibniz's philosophy for years to come. In section 2, we unearth an inconsistency that Leibniz discovered between his first account of substance and the principles, and trace the steps he took in revising the former. In section 3, we argue that this concept of substance, combined with certain theological commitments, led Leibniz to develop most of the central doctrines of his mature thought. For example, we claim that by April, 1676, Leibniz has arrived at his doctrine of preestablished harmony. In section 4, we discuss the relationship between his concept containment theory of truth, which grew out of intensive work on logic in 1679, and his theory of substance. We finally give a brief summary of the central doctrines of the metaphysics of the Discourse.

Leibniz's views on language, and on the relationship of language to philosophy, constitute a rich and, until recently, little explored area of his thought. Unlike some of his seventeenth-century contemporaries, Leibniz was conscious of a deep connection between the human capacity for language and the capacity to comprehend reality. Language is less a barrier between the mind and the world that must so far as possible be overcome than a lens that necessarily intervenes between mind and world and that can, depending on the skill of the optician, either distort or magnify our apprehension of the world. Accordingly, a careful study of language forms an essential part of the method of philosophy.

It is helpful at the outset to distinguish two primary focal points of Leibniz's interest in language. Within his writings these are represented, on the one hand, by the many sketches and plans associated with the notion of an ideal, artificial language - the “universal characteristic”; and, on the other, by numerous historical and philological investigations of natural languages, many of them directed towards uncovering the common roots of a multitude of human languages. On the face of it, there seems to be a tension between the aims and assumptions of these two very different approaches to the subject of language.

Many of the Modern philosophers, most conspicuously Descartes and his followers, seem to have played down their debt to previous philosophy and left little hint as to their background and influences. Leibniz was not in step with this trend towards setting past philosophy aside. He not only regretted the tendency in others but made a practice of locating his own discussions within a broad tradition of philosophical debate. Although he was in his own eyes a Modern philosopher, Leibniz encouraged the revival of the philosophy of the ancients and the selection from it of what was relevant to contemporary problems.' Both in his respect for past philosophers and in his willingness to draw on them in an eclectic manner, Leibniz belonged within the tradition of Renaissance humanism.

Renaissance humanism derived from the fifteenth century but continued right through the seventeenth. It had been stimulated by the discovery of manuscripts and a revival of interest in ancient writings that had long been neglected. The Renaissance philosophers had initially been in reaction against the prevailing academic (Scholastic) philosophy. The Scholastics acknowledged Aristotle simply as “the Philosopher” but, while preserving some Aristotelian terminology, they developed a style of philosophizing that was found to be obscure and unfruitful. Partly in response to Humanist critics, Scholasticism was modified and enjoyed a new lease on life in the late sixteenth century. It continued to be the dominant form of philosophy in the universities of Europe for almost the whole of the seventeenth century.

Understanding the physical world was one of Leibniz's central interests. Earlier chapters of this Companion have explored aspects of Leibniz's metaphysics as they developed, his account of substance in general, and corporeal substance in particular. But Leibniz's interest in the physical world did not stop with metaphysics. Among his writings are numerous letters, notes, essays, and more extended treatments of questions in physics that show his deep engagement with the science of his day. Leibniz was one of the most important physicists of the late seventeenth century; other than Sir Isaac Newton, there is probably no other physicist of his generation who contributed more to the new mathematical physics. Thus, to understand the history of science in this crucial period, we must understand Leibniz's thoughts on physics. For Leibniz, as for many of his contemporaries, there was no clear boundary between philosophy and physics; understanding the world was at issue, and often those involved in what we would call philosophical projects to understand the world were also deeply involved in what we would consider scientific projects as well. Descartes, for example, the great philosopher of the earlier seventeenth century, made important contributions in his writings to mathematics and physics, as did Bacon, Hobbes, Gassendi, and later, Berkeley. Leibniz's physics and his philosophy were deeply intertwined; to try to study the one without the other is to get only a partial and inadequate picture of his thought.

Few philosophers today would go this far. Even in a period that has witnessed a dramatic rebirth of Anglo-American philosophical theology, the typical strategy has been to embrace a favorite proof while criticizing others or to maintain, more cautiously, that a particular argument has not been refuted. Nevertheless, while most of these philosophers reject the claim that all the classic arguments can be rendered sound, they also dismiss as passé the once prevalent view that proving God's existence is a hopeless task.

Natural theology, then, is on the rise. At such a time, it is reasonable to review the arguments of Gottfried Leibniz, one of its most distinguished proponents. Because he thought deeply about many of the issues that now absorb us, an examination of his ideas is likely to illuminate contemporary concerns.

Leibniz gives his own versions of four traditional proofs of God's existence: the ontological argument, the cosmological argument, the argument from eternal truths, and the argument from design. According to the ontological argument, God's existence follows a priori from his definition as an absolutely perfect being. Since existence is more perfect than nonexistence, the very idea of God entails that he exists. The cosmological argument, on the other hand, begins with the fact that something exists and derives the existence of God via a causal principle.

Leibniz claimed to be proud of the fact that, during his lifetime, he had no school, no disciples, and no popularizers. He despised, he said, the sectarian spirit which he associated with the Cartesians. Whether this attitude did not hide a kind of disappointment in the end is open to question. Leibniz was widely admired as a diplomat, a man of learning, and as a mathematician. But he was not, during his lifetime and long afterwards, considered a great philosopher, and after the deaths of Sophie Charlotte, the Queen of Prussia, in 1705, and her mother, the Ellectress Sophie, in 1714, no one showed an intense interest in his metaphysical theories. The dispute with Newton and the Royal Society, followed by the increasingly agitated argument with Newton's representative Samuel Clarke, threw a pall over Leibniz's last two years. Newton, never a gracious opponent, is said to have boasted that he killed Leibniz.

More than twenty years ago, Carl J. Friedrich offered this rather deflationary assessment of Leibniz's significance as a legal and political philosopher - that he was not “a thinker of the first rank on law and politics; no basically novel insight can be attributed to him.” Indeed, it must be admitted that Leibniz followed a traditional Christian reading of the divisions of natural law expounded in the Institutes of Justinian's Code (completed in 529 and revised in 534). It is also true that he resisted the trend toward independent sovereign states in favor of a return to a unified respublica christiana, to be achieved by revitalizing that practically defunct offspring of the medieval marriage of church and state, the Holy Roman Empire. But it must also be said that he developed a profound and inventive philosophical underpinning for the conventional legal wisdom.

Many people first came across the name “Leibniz ” when reading Voltaire's Candide, and the encounter is not likely to inspire confidence in Leibniz as a great philosopher. In Voltaire's biting satire, the optimism of Doctor Pangloss - whose character is based either on Leibniz himself or on his disciples - appears as a foolish and almost wickedly complacent response to the evils of our world. The reader cannot help but sympathize with Candide's rhetorical question: “If this is the best of all possible worlds, . . . what can the rest be like?” Even initial exposure to Leibniz's own texts is not always encouraging. Perhaps the most widely read of Leibniz's works is the Monadology, and although, in many respects, a brilliant summary of his final metaphysical views, it is not the best introduction to his philosophy. It is natural to feel, as Bertrand Russell once did, that we are presented with “a kind of metaphysical fairy tale, coherent perhaps, but wholly arbitrary”; ”art of the problem is that the fairy tale metaphysics is presented to us in a “take it or leave it” manner with little in the way of sustained argument. Initially, then, Leibniz's reputation as a philosophical genius of the first rank may strike us as puzzling.

Problems about the relations between Leibniz's philosophy and his logic have exercised scholars ever since Bertrand Russell's book on the philosophy of Leibniz, first published in 1900. The thesis of that book, as Russell expressed it later, was that “Leibniz's philosophy was almost entirely derived from his logic.” Russell's argument was that Leibniz derived from his logic his distinctive views about the nature of substance - that each substance is a genuine unity, a “monad”; that each created substance expresses the entire universe, and, strictly speaking, does not act on any other substance; that each substance is a soul, or at any rate soul-like; and that no substance resembles any other substance entirely. Russell also discussed Leibniz's views about contingency, about possible worlds, and about freedom. In this volume, Leibniz's views about logic and substance are discussed by Professor Sleigh in a separate chapter; I shall restrict myself to the topics of contingency, possible worlds, and freedom. This is not a haphazard group; there are close connections between Leibniz's discussions of these topics. Nor are the issues raised merely marginal; on the contrary, they take us to the very heart of Leibniz's philosophy.

THE REACTION TO DECARTES

On the basis of their theories of knowledge, early modern philosophers are customarily divided between rationalists and empiricists, with Leibniz following Descartes among the Rationalists, primarily because of his espousal of innate ideas. Whatever one may think of this division of philosophers, Leibniz asserts something very like it. When confronting Lockets Essay Concerning Human Understanding, he remarks:

Leibniz wrote an extensive commentary on and critique of Parts I and I1 of Descartes' Principles of Philosophy, but he has nothing in it to say about innate ideas because in the Principles neither does Descartes. Leibniz, in criticizing the theory of knowledge contained in Part I, of which he is in general highly contemptuous, has no occasion to mention them. Indeed, there is only one thing in the Principles for which he expresses approval: the “I think therefore I am.” This he considers to be “excellent” and relates it to his own distinction between truths of reason and truths of fact. Both kinds have their primitive truths. The first truth of reason is the principle of identity or contradiction.

Ideas play a large role in Locke's philosophy. In Locke's view, everything existing or occurring in a mind either is or includes an idea; and all human knowledge both starts from and is founded on ideas. The very word “idea” appears more frequently in the Essay concerning Human Understanding than any other noun, - its occurrences outnumber even those of such common words as “he” “have,” and “for.”

Locke's ideas have, however, perplexed readers and provoked critics from the time of the Essay's first publication. His contemporary Edward Stillingfleet, the bishop of Worcester, noted the novelty of the term “idea” and charged that Locke's use of it had encouraged “ill men” to take up the “new way of ideas” and use it “to promote scepticism and infidelity, and to overthrow the mysteries of our faith” (W IV: 129-30). Stillingfleet had no objection to Locke's own use of the word, much less to ideas themselves, since he took these to differ only nomine from the “common notions of things, which we must make use of in our reasonings” (ibid.). But John Sergeant, another contemporary critic, found “idea,” as used in the Essay, to be “highly Equivocal, or Ambiguous”; and he argued that in at least one of the meanings assigned it by Locke the word stands for nothing at all, a “meer Fancie” (Sergeant 1697: 3; Preface). This charge of ambiguity, especially, has been a staple of Locke criticism for three centuries: Thomas Reid advanced it, and so did Gilbert Ryle, who wrote, echoing Sergeant, that not only is “the term ‘idea’ . . . used by Locke in a number of completely different senses,” but “there is one sense in which he uses the term . . . in which it must be categorically denied that there are such things as ‘ideas at all. And, ” Ryle continued, “had this been the only sense in which Locke used the term, then his whole Essay would have been, what it is not, a laboured anatomy of utter nonentities” (Ryle 1933: 17).

In the course of its considerable length the Essay concerning Human Understanding deals with many topics; but its main theme and concern is knowledge and the capacity of the human understanding to acquire it. “[M]y Purpose” Locke tells us, is “to enquire into the Original, Certainty, and Extent of humane Knowledge; together, with the Grounds and Degrees of Belief, Opinion, and Assent” (E I.i.2: 43). What is knowledge and how is it acquired? Are there any limits to what we can know and, therefore, things about which we can have only beliefs and things about which we must be ignorant? What, indeed, is the difference between knowledge and belief? As its title indicates, the Essay intends these as questions more about the human knower and believer rather than about what is known and believed. What can we, with our minds, know? In setting out to inquire into knowledge Locke is setting out “to take a Survey of our own Understandings, examine our own Powers, and see to what Things they were adapted” (E I.i.7: 47).

In the background to his questions was a contemporary debate that arose from a large number of arguments against the very possibility of knowledge, arguments that were found in an account of early Greek skepticism, Outlines of Pyrrhonism, written by Sextus Empiricus (fl. A.D. 200). Pointing out that people disagree, these arguments challenge anyone who thinks the truth can be found to say who is its proper judge or real discoverer. Pointing out that our senses are unreliable and our reasonings often mistaken, they ask by what means truth is to be discovered.

John Locke is the most influential philosopher of modern times. His Essay initiated the vigorous and lasting philosophical tradition that is known as British empiricism, but Locke's importance reaches far beyond the limits of what has since his time become recognized as the professional discipline of philosophy. His influence in the history of thought, on the way we think about ourselves and our relations to the world we live in, to God, nature and society, has been immense. His great message was to set us free from the burden of tradition and authority, both in theology and knowledge, by showing that the entire grounds of our right conduct in the world can be secured by the experience we may gain by the innate faculties and powers we are born with. God “commands what reason does” (W VII: n ) are the words that best reveal the tenor and unity of Locke's thought.

THE CORPUSCULARIAN CONCEPTION OF BODY

Locke's treatment of such central philosophical issues as substance, qualities, identity, natural kinds, and the structure and limits of scientific explanation was fundamentally shaped by the conception of body (or as we would say it nowadays, the basic nature of material things) that he inherited from Gassendi and Boyle. This conception of body was part of what Boyle called the corpuscularian hypothesis, or corpuscularianism. This doctrine, a form of mechanistic atomism, had the following core tenets:

1. The matter of all bodies is the same in kind, namely, extended solid substance.

2. All bodies are either (a) individual atoms or corpuscles, which are physically indivisible and which have as their only qualities (in addition to extension and solidity) size, shape, location, motion or rest, and number; or (b) aggregates or collections of atoms. There are no physically real components or constituents of a body beyond its component atoms (except for the material that “glues” the atoms together, if any). Compound bodies have a further quality, their “texture,” which is the arrangement of their component atoms resulting from their various sizes, shapes, relative situations, and relative motions.

3. All changes of state of bodies are due to a change in texture (note that atoms cannot change their size or shape, since they are indivisible); and all changes in texture are the result of impact or contact action of one body upon another. That is to say, all causation involving bodies is mechanical causation.

Locke's failures are sometimes as significant as his successes. His views on morality are a case in point. He published little on the subject, and what little he did publish raised more problems for his readers than it solved. Some of the difficulties contemporaries perceived in Locke's ethics are indicated in a retort by a critic, who was piqued by Locke's suggestion that the critic was part of a plot against him: