For anything to be, Aristotle said, there must already exist a
perfect example to be its cause. This poses the unanswered
question where do these exemplars reside? Also, along the same
line, Aristotle considered the most important cause of the
existence of something to be its final cause, or the reason for
its existence. This is called "Teleological reasoning" because
it presupposes the reason for the existence of anything prior to
the existence of the thing. In natural objects, he said, formal
and efficient (or motive causes, whether natural or artificial
are united in the same individual. For example the efficient
cause of an animal is an animal, because it must be possessed of
the form that will be realized in the offspring. On the other
hand, that of a house is the builder but the form or design must
already exist in his mind. The products of art have their form
in the mind of the artist. He said that the formal, efficient,
and final causes also tend to coalesce in one individual while
the material is likely to be separate. Some causation is
multiple, bronze and the sculpture are both necessary for the
production of a statue. Bronze is matter and sphere is form but
bronze is also the form of a compound with tin and copper being
the materials. Underlying these is the four elements, hot, cold,
earth and air out of which all materials are formed. Still
beneath that he said, in a statement that relates back to
Milesian cosmology, is a substratum that never exists alone but
is the material from which the elements are formed. The elements
can and do change one into another because they are constituted
of this substratum that is common to them all.
However, if we follow this line of reasoning to its logical
conclusion we find the ultimate assumption of the teleologist,
that what underlies the existence of the universe must be an
uncaused cause, and that it must be. That is, it must
necessarily exist, in order that anything else can be. Movement
and causation are used almost interchangeable in Aristotle's
writings which makes sense if you assume that every change is a
movement, and every movement must have a cause. This passage
from Chapter 6, book XII of the
Metaphysics explains why an eternal unmovable substance
is necessary, that is, that its non-existence implies a
Since there were three kinds of substance, two of them physical
and one unmovable, regarding the latter we must assert that it is
necessary that there should be an eternal unmovable substance.
For substances are the first of existing things, and if they are
all destructible, all things are destructible. But it is
impossible that movement should either have come into being or
cease to be (for it must always have existed), or that time
should. For there could not be a before and an after if time did
not exist. Movement also is continuous, then, in the sense in
which time is; for time is either the same thing as movement or
an attribute of movement. And there is no continuous movement
except movement in place, and of this only that which is circular
The Greeks assumed an eternal world that had no beginning and no
end but which was always very much as it is. Yet a creation
myth, a story of the beginning of the world is a part of the
mythologies of all cultures. How can an eternal world be created
or begun? In the Timaeus Plato said that when God created
time he created both future and past. This made time both
eternal and created. In a practical world of real things this
makes little logical sense. Aristotle made a break with Plato
here by stating that time must have been eternal. Also, in a
relation that brings home his attatchment to existing things, he
saw a relationship between time and movement. Remember that
Aristotle was an Ionian grounded solidly in Ionian traditions.
The source of all change and thus the source of all that is in
Ionian tradition was eternal motion. But eternal motion must
either turn back on itself or go on infinitely. It made more
sense to Aristotle if it turned back on itself. Thus, eternal
motion could only be in a circle. Remember that in the
Timaeus Plato too said that perfect motion was necessarily
in a circle, but for a different reason. Aristotle began by
reasoning from actual experience.
But if there is something which is capable of moving things or
acting on them, but is not actually doing so, there will not
necessarily be movement; for that which has a potentiality need
not exercise it.
But an eternal world cannot not be. Its existence is necessary.
Even to think of the world as ever possibly not becoming in the
sense that it may not have ever come into being makes no sense in
an eternal world. The most important of the four Aristotelian
causes was the last, the reason for the thing coming to be.
Potentiality only becomes actuality with a purpose. That which
is only potential not only need not, it will not become actuality
without something additional, a reason for movement. Therefore,
it is not sufficient that the action of the unmoved mover, that
which began all motion, simply be possible, for it would still
then require something else to give it a reason for causing
motion and without that additional something there would be no
Nothing, then, is gained even if we suppose eternal substances,
as the believers in the forms do, unless there is to be in them
some principle which can cause change; nay, even this is not
enough, nor is another substance besides the forms enough, for if
it is not, there will be no movement. Further, even if it acts,
this will not be enough, if its essence is potency; for there
will not be eternal movement, since that which is potentially may
possibly not be. There must, then, be such a principle, whose
very essence is actuality. further, then, these substances must
be without matter; for they must be eternal, if anything is
eternal. Therefore they must be actuality.
The underlying forces that created the universe according to the
Milesians was eternal motion. But this implied something, for
them the arche, that was in motion. It was not set in motion, it
was always in motion. But the arche is nothing but the
underlying substrata. It isn't anything. It just is. That is
it is actual. For actuality is. It does not ever come to be.
It has no need of cause. But for the Milesians the world was the
result of strife among the opposites. It did not have a cause.
There was no thought given to the possibility that the world was
Yet there is a difficulty; for it is thought that everything that
acts is able to act, but not everything able to act acts, so that
the potency is prior. But if this so, nothing that is need be;
for it is possible for all things to be capable of existing but
not yet to exist.
More modern philosophers put it another way. They said that if
anything exists then it is necessary that something exists. But
since, as Aristotle said above, something being capable of
existing does not insure that it will actually exist, either
existence is a quirk of fate, an impossibility in any
Aristotelian sense, or something must exist necessarily. This
something must be unmoving and unchanging. This means it must be
eternal and divine. As developed by Plato and Aristotle the
eternal motion of the Milesians must of necessity turn back on
itself in perfect circles, which is why Aristotle believed that
everything that is has always been but is constantly regenerating
itself. With this background we can continue into chapter 7 of
book XII of the Metaphysics.
There is, then, something which is always moved with an unceasing
motion, which is motion in a circle; and this is plain not in
theory only, but in fact. Therefore the first heaven must be
eternal. There is therefore also something which moves it. And
since that which moves and is moved is intermediate, there is
something which moves without being moved, being eternal,
substance, and actuality. And the object of desire and the
object of thought move this way; they move without being moved.
Desire and thought do not move, they exist already. They already
contain actuality. Desire and thought, though seemingly unmoved
are still caused by something else. Something prior.
The idea that something is moved by desire while desire, being an
object of thought is not moved, seems to be clear enough.
However, desire is the result of thinking and not the other way
around thus it cannot be that which originates movement. What is
capable of originating movement must be the final cause of
thought, the purpose for which thought is originated.
The primary objects of desire and of thought are the same. for
the apparent good is the object of appetite, and the real good is
the primary object of rational wish. But desire is consequent on
opinion rather than opinion on desire; for thinking is the
That a final cause may exist among unchangeable entities is shown
by the distinction of its meanings. For the final cause is (a)
some being for whose good an actions done, and (b) something at
which the action aims; and of these the latter exists among
unchangeable entities though the former does not. The final
cause, then, produces motion as being loved, but all other things
are moved by being moved.
Love provides the ultimate final cause for it moves but is not
moved, it is always the final reason for which any action or
thought is activated. It is the beginning of all movement.
Now if something is moved it is capable of being otherwise than
it is. Therefore, if its actuality is the primary form of
spatial motion, then in so far as it is subject to change, in
this respect it is capable of being otherwise, --in place, even
if not in substance. But since there is something which moves
while itself unmoved, existing actually, this can in no way be
otherwise than it is.
That something, love, exists which moves but is not moved has
been proven. But could it be otherwise? It could not because if
it did not exist then nothing would exist. It is pure love that
produces the eternal movement of the heavens.
For motion in space is the first of the kinds of change, and
motion in a circle is the first kind of spatial motion, and this
the first mover produces. The first mover, then, exists of
necessity; and in so far as it exists by necessity, its mode of
being is good, and it is in this sense a first principle. for
the necessary has all these senses--that which is necessary
perforce because it is contrary to the natural impulse, that
without which the good is impossible, and that which cannot be
otherwise but can exist only in a single way.
On such a principle, Aristotle said the world of nature and all
that we enjoy in it depend for their existence. It is a life
that is the best that we can enjoy and yet for only a short
while. For such a world may be eternal but we are not, but
pleasure is the actuality of the eternal world. Thinking, on the
other hand, deals with that which is best in itself.
If, then, God is always in that good state in which we sometimes
are , this compels our wonder; and if in a better this compels it
yet more. And God is in a better state. And life also belongs
to God; for the actuality of thought is life, and God is that
actuality; and God's self-dependent actuality is life most good
and eternal. We say therefore that God is a living being,
eternal, most good, so that life and duration continuous and
eternal belong to God; for this is God.
Aristotelian science is derived from examining individual things
and developing from those examinations inductive generalizations
concerning the observations. It differs from modern science in
that it does not include experimental manipulation of objects in
order to develop additional insight. Some Aristotelian
assumptions which were to be falsified in the sixteenth century
AD were falsified through such experimentation. These included
such assumptions as the idea that things tend to move toward
where they belong. Thus, heavy objects belong on the ground and
thus tend to move towards the ground while light things like fire
belong in the heavens therefore tend to move up. We will discuss
these problems again when we cover that period.
As you recall Plato's theory of knowledge and his theory of soul
were intimately interrelated. An immortal soul was necessary as
a messenger between the world of the forms and the world of the
senses. Aristotle's theory of knowledge, dealing as it does with
sensible objects, has no need of such an immortal soul. In
De Anima, his treatise on Soul,
his theory of soul was developed only after a long and
complicated argument rejecting all of the ideas of his
predecessors. This section, taken from Book II of
De Anima , show the logical
derivation of his concept of soul.
We are in the habit of recognizing, as one determinate kind of
what is, substance, and that in several senses, (a) in the sense
of matter or that which in itself is not 'a this', and (b) in the
sense of form or essence, which is that, precisely in virtue of
which a thing is called 'a this', and thirdly (c) in the sense of
that which is compounded of both (a) and (b).
This use of purely general terms derived from his logical mind
provides us the opportunity of witnessing the complete
abstraction of essence from the existing. That something is,
that we can talk about it, identify it. That it is something in
itself, for that kind of being we use the term substance. But we
use it in two senses, that something is, that is that we can name
it, and that it is something, that we can identify what it is.
The term substance can be used in either sense. That which
exists in the sensible world is constructed of matter when we use
the term matter as a general term for anything that is corporeal.
Thus the term matter used alone in this way is nothing, but has
the potentiality of being anything that can exist, that is it can
be a substance in the sense that it is something that we can talk
about. But, when we use the term matter we are not suggesting
any particular thing. On the other hand since form is what makes
a thing what it is, it is a substance in the other sense, it
makes what has the potential of being anything a something that
we can identify and talk about. Once form and matter have been
conjoined then what it is conjoined as can not be anything other
than that which it is. Finally, because Aristotle's use of the
term substance is applied to anything we can talk about, we can
use the term substance to indicate that which actually is, that
which includes both the form and the matter and thus a something
Now matter is potentiality, form actuality; of the latter there
are two grades related to one another as e.g. knowledge to the
exercise of knowledge.
Among substances are by general consent reckoned bodies and
especially natural bodies; for they are the principles of all
other bodies. Of natural bodies some have life in them, others
not; by life we mean self-nutrition and growth (with its
correlative decay). It follows that every natural body which has
life in it is a substance in the sense of a composite.
But since it is also a body of such and such a kind, viz, having
life, the body cannot be soul; the body is the subject or matter,
not what is attributed to it. Hence the soul must be a substance
in the sense of the form of a natural body having life
potentially within it. But substance (in the sense of form) is
actuality, and thus soul is the actuality of a body as above
From long-standing Greek tradition the soul of a living thing is
incorporeal, it does not include body. Yet it is, that is it
exists in the sense that we can talk about it. Also, it is
attributed to an existing thing yet is not an attribute of it, it
does not modify what the thing is. It is thus equivalent to
having knowledge rather than exercising knowledge. It also only
applies to that specific entity. And this entity must have life.
Consider the four causes and the implication, particularly of the
final, that they have on what a thing is that is capable of
movement on its own? What defines such a thing is its soul, that
includes everything that makes it what it is including the
quality by which it is capable of self-movement. Thus in such a
body, soul is its form, that which when extracted from it
represents the essence of the thing without being the thing, and
as such is its actuality, but only in the sense that it is what
it is and not in the sense that it is.
Now the word actuality has two senses corresponding respectively
to the possession of knowledge and the actual exercise of
knowledge. It is obvious that the soul is actuality in the first
sense, viz, that of knowledge being possessed, for both sleeping
and waking presuppose the existence of soul, and of these waking
corresponds to actual knowing, sleeping to knowledge possessed
but not employed, and, in the history of the individual,
knowledge comes before its employment or exercise.
That is why the soul is the first grade of actuality of a natural
body having life potentially in it.
That is why we can dismiss as unnecessary the question whether
the soul and body are one; it is as meaningless to ask whether
the wax and the shape given it by the stamp are one, or generally
the matter of a thing and that of which it is the matter. Unity
has many senses (as many as 'is' has), but the most proper and
fundamental sense of both is the relation of an actuality to that
of which it is the actuality.
That means that it is 'the essential whatness' of a body of the
character just assigned. Suppose that what is literally an
'organ', like an axe, were a natural body, its 'essential
whatness' would have been its essence, and so its soul; if this
disappeared from it, it would have ceased to be an axe, except in
name. As it is, it is just an axe; it wants the character which
is required to make its whatness or formulable essence a soul;
for that it would have had to be a natural body of a particular
kind, viz, one having in itself the power of setting itself in
movement and arresting itself. Next, apply this doctrine in the
case of the parts of a living body. Suppose that the eye were an
animal―sight would have been its soul, for sight is the
substance or essence of the eye which corresponds to the formula,
the eye being merely the matter of seeing; when seeing is removed
the eye is no longer an eye except for name--it is no more a real
eye than the eye of a statue or of a painted figure.
As you can see his writing is not as clear as Plato's but it is
more detailed. If soul is the form of a body in the sense that
it is what makes a living thing what it is, then the soul cannot
exist without the body, nor the body without the soul. Plato's
immortal soul and his theory of knowledge were tied together.
Neither could stand without the other. They are each substances
because we can talk about them separately. But when we do this
we extract them from the existing living thing. The soul in
Plato's theory of knowledge was the messenger between the world
of the forms and that of the senses. Now Aristotle has done away
with the world of the forms and no longer has need of an immortal
soul thus his theory of soul is very much in line with the
assumption of particular things as the seat of reality.
Therefore, in order to complete our understanding of Aristotle we
need to understand his theory of knowledge and since this theory
is based on his theory of mind we will turn to that next.