The Birth of a Philosophical System: Leibniz’s Metaphysics, 1677–1686

When Leibniz arrived in Hanover at the end of 1676, he was already an accomplished mathematician and diplomat, but his metaphysics was still in flux. Over the next decade, however, he would develop many of the ideas that later defined his philosophy. Between roughly 1677 and 1686, Leibniz constructed the foundations of a remarkable metaphysical system: a universe grounded in divine wisdom, determined through the divine evaluation of possible worlds and their compossible combinations, and populated by individual substances whose histories are already written into their very concepts.

One of the central questions Leibniz faced was why the world exists as it does. Earlier in the 1670s he had argued that God created the most perfect world possible. Yet reflection on competing philosophies—especially that of Spinoza—pushed him to refine this claim. Spinoza had argued that everything follows from God’s nature with absolute necessity. Leibniz found this troubling because it seemed to eliminate divine freedom and providence. In response, Leibniz developed a subtler position. God knows all possible things, but not all can exist together. Some possibles are incompatible with others, or as he came to put it, some possibles are incompossible (Leibniz also entertained alternative locutions, such as ‘incomponible’ and ‘inconnegible’). Because of these incompatibilities, God must choose among alternative sets of possible things. The actual world exists not because it is logically necessary, but because it is the most perfect combination of possibilities. God chooses it freely, though divine wisdom ensures that the best option is always selected.

This line of thinking led Leibniz to introduce one of his most striking ideas: the doctrine of ‘striving possibles’. Possible things, he suggested, possess a kind of tendency toward existence proportional to their degree of perfection or reality. They cannot bring themselves into existence—only God can do that—but they ‘strive’ in the sense that the most perfect combination of possibilities will naturally recommend itself to the divine intellect. The world we inhabit is therefore the one in which the greatest amount of reality and harmony is realized.

Another major development during these years was Leibniz’s complete concept theory of substance. According to this view, every individual substance—every person, for instance—has a concept that contains all of its predicates: everything that has happened, is happening, or will happen to it. If one understood a substance perfectly, one could in principle deduce its entire history. Leibniz illustrated this idea with historical figures such as Alexander the Great or the apostle Peter: their concepts include not only their birth and death but every action they will ever perform.

At first glance this doctrine seems to threaten human freedom and contingency. If everything about an individual is already contained in its concept, how can actions be free? And if everything is, in some sense, already ‘contained’ in the subject, how can anything be genuinely contingent? Alive to the concerns, Leibniz’s initial recourse was to his formula that ‘reasons incline without necessitating’. In contingent truths, he argues, we can give reasons why something happens, and these reasons make the outcome certain without making it logically necessary. In other words, the opposite remains possible. What is especially striking is that this formula is an adaptation of a well-known Renaissance proverb: ‘the stars incline, they do not necessitate’. By replacing ‘stars’ with ‘reasons’, Leibniz transformed a familiar saying about astrology into a powerful philosophical principle. This allowed him to present a subtle and innovative idea in terms his contemporaries would immediately recognise. The result is a framework in which God’s choices—and human actions—are both intelligible and free: guided by reasons, yet not compelled by them. The formula was later supplemented by Leibniz’s recasting of contingency in terms of infinite analysis: while the predicate is contained in the subject in the case of both necessary and contingent truths, in the former case only a finite analysis is required to demonstrate the connection, whereas in the latter an infinite analysis is required.

During the same period Leibniz also began developing the doctrine that would later become known as pre-established harmony. Rather than interacting causally, substances unfold their states according to their own internal principles. God arranged things from the beginning so that the states of all substances correspond perfectly, giving the appearance of interaction. The mind and body, for example, do not directly affect each other; instead, their states run in perfect synchrony according to divine design.

These ideas were often developed in brief notes and fragments, many of them scribbled on scraps of paper. By 1686, Leibniz had enough of the philosophical pieces to attempt a more systematic presentation, resulting in a lengthy essay he left untitled, to which scholars almost two centuries later gave the title ‘Discourse on Metaphysics’.

English translations of seventy-three of Leibniz’s metaphysical writings from this formative decade of his philosophical thought are collected in the new 3-volume edition of Leibniz’s Philosophical Papers 1677—1686.

— Lloyd Strickland, 31.iii.2026

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