Hao Dong

I examine Leibniz's philosophy, both early and mature, from a methodological and structural point of view. Leibniz's philosophical methodology is shown to have received significant influence from that of Hobbes, whose natural philosophy consists of a demonstrative, necessary part and a hypothetical part. I argue that the same holds for Leibniz and that Leibniz consistently constructs his philosophical system based on his methodology. The most important consequence that I draw from this is that the mature metaphysics of Leibniz, namely his metaphysics of monads, is most likely a hypothesis.

In this paper I argue that Leibniz's ethics is a kind of virtue ethics where virtues of the agent are explanatorily primary. I first examine how Leibniz obtained his conception of justice as a kind of love in an early text, Elements of Natural Law. I show that in this text Leibniz's goal was to find a satisfactory definition of justice that could reconcile egoism with altruism, and that this was achieved through the Aristotelian virtue of friendship where friends treat each other as “other selves.” Following this decisive moment, Leibniz adopted an Aristotle‐inspired ethical framework where the virtuous agent is central for moral evaluations. I then show that, despite certain developments, Leibniz's ethics retained this essential feature throughout his career. In Leibniz's later writings, God constitutes the foundation of the moral realm, and the fundamental moral endeavor of human beings consists in the imitation of God.

In this paper I argue that there is a structural parallelism between law and physics in Leibniz since his early years, which has significant influence on the formation of his views. I start by examining Leibniz's early physical system and an analogy with juridical laws that he uses to explain the structure of physical laws. Then, I argue that this analogy stems from an envisioned parallelism between law and physics. Finally, I illustrate the significance of this legal-physical parallelism by arguing that it underlies some of Leibniz's mature views. Most importantly, I argue that the parallelism explains the origin of architectonic principles or optimality principles in Leibniz's mature physics.

This paper aims both to tackle the technical issue of deciphering Hobbes’s derivation of the sine law of refraction and to throw some light to the broader issue of Hobbes’s mechanical philosophy. I start by recapitulating the polemics between Hobbes and Descartes concerning Descartes’ optics. I argue that, first, Hobbes’s criticisms do expose certain shortcomings of Descartes’ optics which presupposes a twofold distinction between real motion and inclination to motion, and between motion itself and determination of motion; second, Hobbes’s optical theory presented in Tractatus Opticus I constitutes a more economical alternative, which eliminates the twofold distinction and only admits actual local motion, and Hobbes’s derivation of the sine law presented therein, which I call “the early model” and which was retained in Tractatus Opticus II and First Draught, is mathematically consistent and physically meaningful. These two points give Hobbes’s early optics some theoretical advantage over that of Descartes. However, an issue that has baffled commentators is that, in De Corpore Hobbes’s derivation of the sine law seems to be completely different from that presented in his earlier works, furthermore, it does not make any intuitive sense. I argue that the derivation of the sine law in De Corpore does make sense mathematically if we read it as a simplification of the early model, and Hobbes has already hinted toward it in the last proposition of Tractatus Opticus I. But now the question becomes, why does Hobbes take himself to be entitled to present this simplified, seemingly question-begging form without having presented all the previous results? My conjecture is that the switch from the early model to the late model is symptomatic of Hobbes’s changing views on the relation between physics and mathematics.