Stony Brook University

Now we can turn to Locke’s argument on innate practical principles. His
argument can be summarized as follows: If there are such principles, then the following
conditions necessarily obtain:
(1) Innate practical principles hold true for everyone, even if not universally
practiced.
(2) They are universally assented to (agreed upon as valid).
(3) They must be, or must have been, consciously known to the agent.
(4) They effectively regulate, motivate, or guide our actions.
Locke argues, however, that conditions (2), (3), and (4) do not obtain, and so he
concludes that innate principles do not exist. Both Leibniz and Locke agree on (1), since
they agree that practical principles are valid for everyone. They also agree that innate
principles are demonstrable, although for Locke this proves they are not innate, while for
Leibniz this simply means they are not immediately known, but can be discovered. They
also agree on one sense of ‘innate principle,’ that is, as a sensual, motivating instinct,
although we must be careful to distinguish different senses of ‘instinct,’ as we will see.
Leibniz does not, of course, accept Locke’s conclusion that innate principles do not exist.
He argues that innate principles, including practical ones, exist, that they do effectively
motivate our actions (if not always), but need not be consciously known nor assented to.
Now let us examine the details of Locke’s arguments against innate practical
principles, beginning with his understanding of what innate practical principles is
supposed to be. They are not exactly the mathematicians’ common notions, but rather
“those common notions written on our minds by the finger of God” (E 1.2.16). Quite
likely, Locke is obliquely referring to, and thus criticizing, St. Paul’s often-cited dictum:
“They [the gentiles] show the demands of the law are written in their hearts.” 8 However,
Locke claims that the case for the innateness of such principles, characters, or notions is
much weaker than it is for speculative principles. To begin with, practical principles lack
self-evidence, since they require “reasoning and discourse, and some exercise of the
mind, to discover the certainty of their truth” (E 1.2.1). In other words, if becoming aware
of their truth requires a demonstration, they cannot be innate.
I will return to the issue of demonstration, but first we must distinguish between
two senses of ‘principle’ which Locke (and Leibniz) often employ here. A demonstrative
principle is one sense in which Locke understands “principle,” that is, as a self-evident
proposition suitable for demonstrations. The second sense of ‘principle’ is as a source of
action, i.e., as the motivating force within a thing—in this case either an instinct or a
conscious thought that moves one to act. It is important to bear in mind both of these
senses in what follows.
Locke argues that if there were innate practical principles, they would (1) be
consciously recognized and assented to; and (2) they would effectively motivate or
regulate our actions. But neither case holds. As for (1), innate principles should be
immediately known and recognized, but yet, “the ignorance wherein many men are of
[moral principles], and the slowness of assent wherewith others receive them, are
8 Romans 2:15. As Jerome Schneewind claims, “Every theorist of natural law from Aquinas onward had
cited this passage as an authoritative warrant for the claim that there is a moral law discoverable by reason.
But Locke seemed to be dismissing St. Paul” (SL 201).
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