Stony Brook University

Accordingly, the perfection of the will leads to the perfection of society. In this way we
may understand that the metaphysical requirement for the best possible world has its
foundation in the moral nature of rational substances, and has its theoretical foundation in
the science of right.
Section 5: Dissertation summary of conclusions
I conclude this dissertation with a brief chapter-by-chapter summary of its main
claims and findings. Beginning with Leibniz’s Nova Methodus Discendae Docendaeque
Jurisprudentiae (1667), I focused on the definitions of right and obligation. Right (ius) is
the moral power (potentia moralis) of a rational substance, and obligation (obligatio) is
its moral necessity. Right and obligation thus denote the deontic “moral qualities” that
enable a rational substance to act justly and to demand justice from others. A just act is
that which promotes public utility. From this definition, Leibniz derives many others,
most importantly, the three precepts or degrees of right (juris gradus). These are harm no
one, give to each his due, and live honorably. These precepts, actually borrowed from the
Roman Digest, and said to be the logical consequence of the definitions of right and
obligation. I further showed that the objective requirements of the just (public utility) are
also derived from this foundation of right. I should emphasize that the foundational
importance of these definitions and their connection to the three precepts of right has not
been analyzed at all in existing commentary on Leibniz. As I have argued, without
understanding this foundation, Leibniz’s practical philosophy cannot properly be
understood. This foundation must not be understood as deriving from the motives of love
(either egoistic or non-egoistic), pleasure, happiness, or perfection. The foundation of
right is deontically prior to these motives, and it provides the conceptual basis for the
notions of freedom and necessity that pervade Leibniz’s moral and metaphysical thought.
In Chapter Two, the detailed and extensive examination of the Elementa Juris
Naturalis (1669-71) led to two important developments for Leibniz: the introduction of
the notion of practical love into his theory of right, and his invention of a deontic or
“juridical” mode of logic. My most important claim is that Leibniz introduces the notion
of love as a descriptive motivational principle, so that the prescriptive (normative)
demands of right may be fulfilled. The cause of this introduction is Leibniz’s attempt to
defeat the skeptical claim that justice either does not exist or it is folly, since it either
enjoins us to do another’s good (which no one would do) and to do it at one’s own
expense (which is foolish). Two points are most important to be clear on: (1) Leibniz’s
argument for the nature of justice as love, and the nature of love as pleasure, 38 seems to
land him squarely upon hedonistic foundations. However, I argue that if ,pleasure is
understood as fulfilling a psychophysical requirement for action, and that pleasure is the
result but not the end of acts of justice, then the foundation, the a priori foundation is
built squarely upon right. (2) The investigation of the terms right, just, and justice should
lead us to pay careful attention to the distinct meaning and role of each of these terms in
Leibniz, a point often missed by commentaries and translators: right (ius) is the moral
power to do what is just; the just (iustum) is defined as an “equitable” relation between
own and other good; and justice (iustitia) is the virtue of loving everyone justly. Leibniz
believes that he arrives at these true definitions solidly by means of his epagogic
38 Recall his definition of love: “To love is to find pleasure in the pleasure of another.”
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