Stony Brook University

fundamentally no more than aides to reason and indications of nature’s
plan. Custom, education, tradition, reason contribute a great deal, but still
human nature plays its part; though without reason these aids would not
suffice to make [moral doctrine] completely certain. (NE 1.2.9.94) 71
The key point is that no non-rational motivating factor is sufficient for attaining certainty
about moral doctrine; only reason can provide that. His claim, therefore, is that it should
not be surprising that people often do not follow what reason commands, or that they do
follow it without knowing it, since both the awareness and motivational power can be
obscured by other factors. In the end, moral certainty depends on reason.
What can we conclude at this point regarding the natural law commanded by
reason and the natural law consisting of instinct? And what implications are there for
moral doctrine as a demonstrable science? It appears that the natural law of the Gospel
(the double command of love) forms the foundation of moral doctrine. However, Leibniz
himself does not explicitly say this. Therefore, we must conclude that we do not have
demonstrative knowledge of the foundation of moral doctrine. On the other hand, we
have come across quite a variety of non-conscious motivating factors, of the kind
associated with the natural law of the Digest. These can perhaps be best described as a
general social instinct. The role of these instincts is to serve as aids to indicate “part of
what reason commands.” In addition, we have seen that passions, prejudices and
“contrary customs” can distort naturally good instincts. Locke is much more critical of
instincts, if what is meant by instinct is ‘a general appetite or inclination for the good’:
“Principles of actions indeed there are lodged in men’s appetites; but these are so far
from being innate moral principles, that if they were left to their full swing they would
carry men to the overturning of all morality” (E 1.2.13). Leibniz just seems more
confident that instincts for the most part lead us in the right direction; nevertheless, they
are ultimately not reliable moral principles. For these reasons the instincts can only
provide partial assurance that our actions will conform to the commands of reason, and
they do not tell us sufficiently what reason commands. Therefore, instincts cannot be the
justificatory foundation of moral doctrine. In neither case, either through commands of
reason or instinctual impulses, does Leibniz provide any certainty about moral doctrine.
We can summarize the issues we have encountered so far by taking a look at one
more passage from the chapter on innate practical principles. Locke is shown to claim
that “the law of love and care for children was violated by the ancients when they
permitted exposing them” (NE 1.2.12). Therefore, they must not have had such a law of
love. Leibniz replies,
Granting this violation, all that follows is that we have not always
correctly read the characters which, though nature has engraved them in
our soul, are sometimes veiled by our licentiousness. In any case, to have a
compelling view of the necessity of one’s duties one would have to grasp
a demonstration of it, which seldom happens. If geometry conflicted with
71 A.6.6.94: “Mais dans le fonds ces impressions naturelles quelles qu’elles puissent estre, ne sont que des
aides à raison et des indices du conseil de la nature. La coustume, l’education, la tradition, la raison y
contribuent beaucoup, mais sans la raison ces aides ne suffroient pas pour donner une certitude entiere à la
morale.”
192