Western Philosophy. Pythagoras may already have
been a dualist, in two senses. On the one hand, the
Pythagoreans taught that all things are composed of
contraries: the one and the many, the limited and the
unlimited, the odd and the even, right and left, mascu-
line and feminine, rest and motion, the straight line
and the curve, light and darkness, good and evil, etc.
Now, these opposites seem to have been the various
forms of a single fundamental relation of contrariety.
On the other hand, they distinguished profoundly soul
and body, as is shown by their theory of the transmi-
gration of souls and by the dictum attributed to them
as well as to the Orphics: “The body is a tomb.”
Heraclitus and Parmenides appear to have attacked
pythagorean dualism, at least the dualism of contraries.
Heraclitus showed that the contraries are inseparable
and form a unity; Parmenides proclaimed that only
the one, immobile, eternal Being exists, whereas the
many, the moving, perishable things do not exist in
true reality.
Empedocles, on the contrary, continued to maintain
the two Pythagorean kinds of dualism. For him the
world is dominated alternately by two opposing prin-
ciples, Love and Hate, which produce respectively
unity and multiplicity. Furthermore, the soul for him
has a different nature than the body, and he tells of
a soul which, having fallen from the world of the gods,
moaned at seeing itself in “this unaccustomed place”
(frags. 118, 119).
Anaxagoras, in his turn, clearly distinguished two
kinds of beings: elements in general, that are mixtures
in which everything is mingled with everything else,
on the one hand, and on the other, the mind (voūs)
which alone exists apart, is pure, without admixture,
and which, on coming into the chaos of the elements,
puts order into them.
Plato does not teach any dogmas, but his dialogues
tend to support the view that the soul exists inde-
pendently of the body and that the intelligible world
is independent of the world perceived by the senses.
It is true that the latter world cannot be said really
to be, for only the intelligible, the Idea, constitutes
true Being. Yet the world of sense has also a kind of
existence. In the myth of the creation of the world,
the Demiurge, the good “Worker,” is not the only
cause of the universe; there is also another cause,
namely, Necessity. The Demiurge “persuades” Neces-
sity to direct most things towards the Good, but its
power is not unlimited (Timaeus 47e-48a). In the Re-
public (379b-380c), Socrates says that God is not the
cause of everything, but only of what is good. In the
Theaetetus (176a), he says: “It is necessary that there
should always be something contrary to the good.”
It has sometimes been supposed that Zoroastrianism
influenced Pythagorean and Platonic thought, but it
is hardly probable. The wicked soul mentioned in
Plato's
Laws (896e-898c) does not appear as a cosmic
soul, and in the
Statesman (270a), he repels the idea
that the world could be governed by two opposing
deities. Moral evil, for Plato, is due to the ignorance
produced in the soul by its union with the body.
Aristotle is much more of a monist than his teacher
Plato, whom he criticizes for having “separated” the
Idea from sensible things. He tries to restore a continu-
ity between the lower and the higher life; matter is,
for him, already potentially what form is in actuality.
He ties the soul in an intimate relationship to the body
when he defines it as the form or entelechy of a natural
body potentially possessing life. Yet there remains in
Aristotle something of the Platonic dualism, particu-
larly in his theory of the prime mover, an incorporeal
and separate substance; also in his theory of the intel-
lect which he seems to hold as separate from all the
other faculties of the soul, entering it as though it were
from the outside.
After Aristotle the Stoics and Epicureans are more
thorough monists, the first school having a spiritualistic
monism according to which the whole world is mind
or reason, the second having a materialistic monism
which reduces everything to atoms.
Christian philosophy at first leaned principally on
Plato, but from the thirteenth century onwards, theo-
logians made use chiefly of Aristotle, not without
modifying some of his theories in order to bring them
into harmony with Christianity.
In the Renaissance period Plato returned, and with
him dualism was revived. In the seventeenth century
Descartes sharply divided reality by defining mind
exclusively as a substance that thinks, and matter ex-
clusively as an extended substance, thus distinguishing
them radically from one another. This distinction,
which excludes any intermediary, allowed Descartes
to establish a clear, wholly mathematical science of
physics. Every fact in the material world was to be
explained solely by geometry and mechanics.
Descartes' successors did not tolerate this bifurcation
of reality into two substances. Spinoza made extension
and thought no longer two substances but two attri-
butes of the one substance God. Leibniz, although he
distinguished in a certain way the soul from the body,
pictured all reality on the model of thought.
Kant, in his chapter of the Critique of Pure Reason
entitled “Paralogism of the Ideality of the External
World” (Transcendental Dialectic, Book II), criticized
dualism insofar as it signified that thinking substance
and extended substance are things in themselves, but
he admitted it insofar as it could signify that subject
and object are quite distinct phenomena. To this divi-
sion within phenomena he added the distinction of
phenomena and things in themselves. For Kant there
are somehow two worlds: one is the world of phenom-
ena and the other, known only through consciousness
of moral duty, is reality in itself.
Philosophers coming after Kant tried to do away
with these profound divisions. Fichte made the free
subject the basis of everything, the ground for the
existence of the universe. Hegel brought the whole of
reality into a single chain by making contradiction, first
posited and then transcended, the law of all thought
and of all nature.
Thus the history of Western philosophy appears to
be an alternation of dualism and monism. On several
occasions philosophy has been renovated by a very
dualistic doctrine: Platonism, Cartesianism, and
Kantianism have initiated such renovations. However,
dualism was soon overcome and submerged by more
or less monistic doctrines. The teacher is a dualist, but
his pupils are not. It seems as though there was some-
thing too harsh and rough in dualism for most philoso-
phers to bear. They wish to reconcile everything, and
dualism disappoints them by the very fact that it posits
two principles and not one alone. They believe that
dualism is a failure, that it does not succeed in unifying
all of reality; they expect philosophy to unify every-
thing. But the dualistic philosophers have perhaps
judged that the human condition requires us only to
think and act well in the present; they have tried,
above all, to justify the clearest method of thinking
and the most certain morality. To confuse the body
more or less with thought is to lodge in the body a
mysterious force, which is impenetrable to clear sci-
ence, and which destroys the will to govern the body.
In our own twentieth century, Lovejoy has de-
scribed, under the title The Revolt Against Dualism,
the many attempts of contemporary philosophers to
refute or to avoid dualism; he believes that they have
all failed. Alain (1868-1951) has taught the moral value
of dualism in Cartesianism and maintained that dualism
is not a fault in a philosophy but, on the contrary, is
the most vigorous trait, revealing the energy which
makes sound thinking. Philosophical dualism does not
imply the condemnation of certain beings outside one's
self, but expresses a will to govern one's self.
