Stony Brook University

in Chapter Two.
The Nova Methodus consists of two parts: Part I (which I discuss only briefly)
outlines a “psychology and philosophy of education.” 5 Part II (which I examine at length)
attempts to systematize the philosophical foundations of law, or in other words, to
establish a “science of jurisprudence.” This science will be seen to consist most generally
of a Euclidean method, i.e., to begin with definitions and from them to derive the precepts
of natural right. More specifically, this science consists of the definitions of
‘jurisprudence’, ‘the just’, ‘morality’ (moralitas), ‘right and obligation’ (jus and
obligatio), along with a number of associated terms. The derived precepts are harm no
one, give to each his due, and live honorably. In this way, borrowing largely from Euclid,
Grotius, and Roman law (and at a deeper level, Aristotle), Leibniz establishes the a priori
foundations of natural right, as well as a science for the judgment of the jurisconsult. The
claim that jurisprudence is an a priori science is essential for Leibniz, since only as an a
priori science can jurisprudence be a truly demonstrative, and thus a certain and universal
science, by which actions can be determined just or unjust. This attempt to establish a
priori foundations remains characteristic of all of Leibniz’s subsequent thinking on the
foundations of justice and morality, indeed, on the whole of his practical philosophy, as
will be shown.
Leibniz’s science of jurisprudence has an extremely important consequence,
although he does not make this consequence entirely explicit. The definitional structure
of this science reveals that jurisprudence, encompassing as it does, justice, morals,
natural law, and even theology, is grounded in the moral qualities of right (jus) and
obligation. These are the moral qualities of a rational substance (substantia rationalis).
Right is the “moral power” (potentia moralis) of a rational substance (i.e., God or a
human); and obligation is the “moral necessity” of a rational substance. Thus, the
concepts of right and obligation denote the deontic properties of moral agents, the
properties enabling the subject to act according to the good (public utility). In other
words, right and obligation constitute the subject’s self-limiting power and freedom to be
a moral agent. In contemporary terms, this notion of right is called “subjective right.” In
short, jus is the central grounding concept of Leibniz’s practical philosophy. This claim,
which is a major claim of the dissertation, may at first glance appear strange and
controversial. Nevertheless, I maintain that only on the conception of right that Leibniz
develops here can the nature and development of his practical philosophy as a whole be
properly understood. 6
Section 2: General Remarks on Parts I and II of the Nova Methodus
Part I of the Nova Methodus contains, among other things, several key points for
understanding the work and Leibniz’s practical philosophy in general. I begin with the
subheading and first sentence:
Part I: General and Common to All other Faculties: On a plan for Studies
in General.
5 See Loemker’s introductory remarks, p. 85.
6 As I will show, Leibniz’s moral philosophy, which, as everyone recognizes, contains hedonistic,
utilitarian, and egoistic elements, is incomplete and misunderstood without his theory of right.
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