Stony Brook University

CHAPTER FIVE: MORAL DOCTRINE AS A DEMONSTRATIVE SCIENCE IN THE NOUVEAUX
ESSAIS
Chapter sections:
1. Introduction
2. Locke on innate speculative and practical principles
3. Leibniz on innate practical principles
4. Moral doctrine, pure reason, and the science of right.
5. Integration of principles in virtue
6. Chapter conclusion
“I warmly applaud what you have just said, sir, about morality as a
demonstrative science” (NE 89). 1
“This is how we are led to act humanely; by instinct because it pleases us,
and by reason because it is [just]” (NE 91). 2
“As for morality: one part of it is wholly grounded in reasons, but there is
another part which rests on experiences and has to do with [people’s]
temperaments” (NE 352). 3
Section 1: Introduction to chapter
Leibniz’s engagement with Locke on innate practical principles in the Nouveaux
Essais (1704) provides fruitful insight into the foundations of Leibniz’s practical
philosophy. We will find that the foundation can be divided into two kinds of principle:
(1) principles that are sources of activity or motivation, such as the principle of pleasure
and pain and other instincts; (2) principles that are sources of justification for an action,
such as those having to do with right, justice, and “pure reason.” This division
corresponds with Leibniz’s frequently made distinction between truths of fact and truths
of reason. Making this distinction enables us to clarify Leibniz’s claim that moral
doctrine (la Morale) is a demonstrative science. The result will be, or so I argue, that the
principles of instinct are descriptive principles of human behavior, as well as initial
indicators of what is morally prescribed. While we can make sense of Leibniz’s claim of
demonstrability in respect to them, these principles are not strictly demonstrable. On the
other hand, what is morally prescribed is determined by the theoretically demonstrable
principles of reason. Yet it remains difficult to determine what principle of reason serves
as a moral prescription. However, Leibniz does offer, or so I suggest, the best possibility
for a grounding of moral doctrine in the science of right. In sum, by investigating these
1
A.6.6.89: “Et j’applaudis extremement à ce que vous venés de dire, Monsieur, de la morale, comme d’une
science demonstrative.”
2
NE says ‘right,’ not just. A.6.6.91: “C’est ainsi que nous sommes portés aux actes d’humanité, par instinct
parce que cela nous plaist, et par raison parce que cela est juste.”
3
A.6.6.352: “Pour ce qui est de [la] morale, une partie en est toute fondée en raisons, mais il y a une autre
qui depend des experiences, et se rapporte aux temperaments.”
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