580 GOTTFRIEDLEIBNIZ
At his death, he left an enormous number of unpublished letters and manu-
scripts. One major work was published in 1765: his detailed critique of Locke’s
Essay,entitled Nouveaux essais sur L’entendement humain. Leibniz had com-
pleted the book in 1704 but withheld it from publication when Locke died the
same year. The book greatly stimulated Immanuel Kant, particularly his Critique
of Pure Reason. In the twentieth century, thinkers such as Bertrand Russell and
Ernst Cassirer have focused attention on Leibniz’s work in logic. The neglect of
Leibniz in his lifetime has given way to the current great admiration for the scope
and originality of his thought.
Leibniz’s philosophy begins by rejecting the notion that extension is a substance
(as Descartes claimed) or an attribute of substance (as Spinoza thought). Instead
of understanding nature as a collection of discrete extended entities, such as
atoms, Leibniz says that the basic substance is a “Monad,” or a unit of psychic
force. Such Monads are without parts (i.e., simple) and have no interaction with
one another. As Leibniz puts it, they have “no windows through which anything
may come in or go out.” Each Monad has within itself an internal principle of
“appetition” that causes it to change. Although there is no causal interaction
between Monads, they may appearto influence one another. This connection is
merely a reflection of the “pre-established harmony” by which God created each
of the Monads to “mirror” the others. A Monad’s entire past and present are con-
tained within it so that whatever it does, it does so by necessity. If we could know
the entire past of a given Monad, we could predict its entire future.
Monads all differ qualitatively and occupy different points of view. This means
that each Monad “mirrors” the world in a slightly different way and with different
levels of clarity. Rocks and dirt are made of colonies of “low-level” Monads that
have only dull and confused perceptions as they mirror the world. It might seem
odd to talk about rocks as having perceptions at all, but according to Leibniz,
every Monad has some sort of psychic life: Each Monad has an “internal state [by
which it] represent[s] external things.” Those Monads whose perceptions are
“more distinct and are accompanied by memory” are on a higher level. The dom-
inant Monad of an animal, for example, has distinct perceptions and memory of
those perceptions: “If you show a stick to a dog, for instance, it remembers the
pain caused by it and howls or runs away.” This dominant Monad Leibniz calls a
“soul” to distinguish it from lower level or “naked” Monads. Human beings are
Monad aggregates of yet a higher degree. Whereas human bodies are colonies of
lower Monads, the dominant Monad in a person is a “spirit,” because it is capable
of performing “reflective acts.” Spirits are also capable of knowing the universe
and of entering into a relationship with the chief Monad, God.
Leibniz’s metaphysics seems to exclude the possibility of freedom. If each
Monad has its entire future within it, and if it thus unfolds that future by necessity,
how can we, as colonies of a dominant “spirit” Monad and lower “body” Monads,
be free? Leibniz’s answer to this question turns on his definition of “freedom.” To
be “free,” claims Leibniz, does not mean “liberty of indifference.” Instead we are
“free” in that our actions flow from our wills and there is no logical contradiction
in our willing other than we do. As Leibniz put it, “there is always a prevailing
reason which prompts the will to its choice, and for the maintenance of freedom
