but these causes explain nothing as to why death should
be in the world at all. Now if we accept this distinction, we
may say that Aristotle’s conception of causation includes
both what we have called causes and reasons. Whatever
is necessary, whether facts or principles, whether causes or
reasons, fully to understand the existence of a thing, or
the happening of an event, is included in the Aristotelian
notion of causation.
Taking causation in this wide sense, Aristotle finds that
there are four kinds of causes, the material, the efficient,
the formal, and the final cause. These are not alternative
causes; it is not meant that, to explain anything, one or
other of the four must be present. In every case of the
existence or production of a thing all four causes operate
simultaneously. Moreover the same four causes are to be
found both in human and in cosmic production, in the mak-
ing of manufactured articles by man and in the production
of things by nature. They are more clearly and easily seen,
however, in human production, from which sphere, there-
fore, we select our example. The material cause of a thing
is the matter of which it is composed. It is the raw material
which becomes the thing. For example, in the making of a
bronze statue of Hermes, the bronze is the material cause of
the statue. This example might lead one to suppose {269}
that Aristotle means by material cause what we call mat-
ter, physical substance, such as brass, iron, or wood. As
we shall see later, this is not necessarily the case, though it
is so in the present instance. The efficient cause is always
defined by Aristotle as the cause of motion. It is the energy
or moving force required to bring about change. It must
be remembered that by motion Aristotle means not merely
change of place but change of any sort. The alteration of
a leaf from green to yellow is just as much motion, in his
sense, as the falling of a stone. The efficient cause, then, is
the cause of all change. In the example taken, what causes
the bronze to become a statue, what produces this change,
is the sculptor. He is, therefore, the efficient cause of the
statue. The formal cause Aristotle defines as the substance
and essence of the thing. Now the essence of a thing is given
in its definition. But the definition is the explication of the
concept. Therefore the formal cause is the concept, or, as
Plato would call it, the Idea of the thing. Plato’s Ideas thus
reappear in Aristotle as formal causes. The final cause is
the end, purpose, or aim, towards which the movement is
directed. When a statue is being produced, the end of this
activity, what the sculptor aims at, is the completed statue
itself. And the final cause of a thing in general is the thing
itself, the completed being of the object.We can see at once how much wider this conception of cau-
sation is than the modern conception. If we take Mill’s def-
inition of a cause as the best expression of modern scientific
ideas, we find that he defines a cause as the “invariable and
unconditional antecedent of a phenomenon.” This cuts out
final causes at once. For {270} the final cause is the end,
and is not an antecedent in time. It also does not include
formal causes. For we do not now think of the concept of
a thing as being part of its cause. This leaves us with only
material and efficient causes, and these correspond roughly
to the modern notions of matter and energy. Even the effi-
cient causes of Aristotle, however, appear on further consid-