Caitlin
Griffith
Dr.
John Goyette
Theology
4
November 2012
The
Universal Necessity of a Mover Derived from the First Way
In Thomas’ first
way, he argues to a necessary first mover using the more immediate knowledge of
potency and act taken from the Aristotelian definition of motion. With these
terms he determines two principles; everything moved must have a mover, and the
thing actualizing the potency must be separate from the thing being actualized.
Though it seems that one could counter Thomas’ proof with examples of self-movers,
it is not so, because to be in motion, these apparent self-movers must also abide
by these two principles, and therefore they too need their respective movers.
Thomas begins what
he calls the most manifest of the five ways by stating that it is clear that
some things in the world are in motion. This is motion in the sense of all change
in nature – everyone can induce from the rising and setting of the sun, the
change in the color of the trees, and man’s own change over his own life, that
there is motion in nature. He speaks of this change in nature in terms of
potency and act because he wants to use these terms of the Aristotelian
definition of motion to establish a case for the first mover. He wants to start
with two terms whose definitions don’t already imply motion because their non-motive
nature makes them better known and more immediate in the science than motion of
itself. An analysis of this first premise results in two middle terms of the
full argument, one, that everything moved must have a mover, and two, that this
mover must be a separate one.
It is important
for the soundness of the conclusion of the whole first way to understand how
these middle terms of the argument follow from the Aristotelian definition of
motion, ‘the act of that which exists in potency insofar as it is such’
(Physics 3.1). This definition that
distinguishes potency and act is what lets Thomas argue that potency cannot
actualize itself, i.e. nothing can be its own mover. For from this distinction
between potency and act that underlies Aristotle’s definition of motion, one
can know that motion necessitates a conceptual difference between what is in
act, the mover, and what is in potency, the object moved. In the concept of
motion, there must always be something reducing the potency to act, and
something being reduced from potency to act.
Now Thomas must
establish that these two factors must be separate, i.e. that the mover and
moved cannot be one in the same respect. So he says that the potency cannot
actualize itself because to actualize anything, it would have to already be in
act. But clearly from the Aristotelian understanding of the term, potency is
not something that ever actually exists. Therefore, by its own nature, potency
cannot actualize itself. This idea is behind Thomas’ comment that
nothing can be reduced from potency
to act, except as being in act, as the hot in act, such as fire, makes wood,
which is hot in potency to be hot in act, and thereby moves and alters it.
Motion necessitates a potency that is
capable of being actualized (because there must be somewhere/something to move
toward), and the actual state and the potential ‘after motion’ state remain
separate without a mean to bring them together. This mean is motion, the
imperfect act that shares in both the act and the potency of the thing.
Thus, motion has
an intrinsic antagonism between what is in act and what is in potency. If they
can never be one in the same respect at the same time, then for anything to be
moved, there must be always be something other.
Motion can not begin itself; it is essentially reactive. This understanding of
its reactive nature follows from the Aristotelian term of potency and act.
Objectors to the
first way may raise may say that there are examples of self-movers like the
will and the projectile once it has left its source of motion. But the
distinction between what is in potency and act also applies in these cases, and
therefore Thomas’ first way withstands such objections.
It appears that
some things, like animals, can move themselves, for from experience it seems that
we move ourselves. A man’s actions will stem from the impetus of the will.
Still, the will, which appears to be at rest (and thus an unmoved mover)
compared to that which it moves, cannot actualize itself. One can know this because we see first
of all that the will can and does move, because animals discern and choose
between different options. But anything that moves has to have a beginning
(potency to act) and an end (actuality of potency) of motion. If the will were
self-actualizing, it would always be in act, because the end and the beginning
of the motion would be united in itself. But clearly the will is not always in
act, because it does not always will one way or another, but changes. Therefore
the will is not self-actualizing. It still seems one can call animals
self-movers in a less strict sense though because an animal’s motion can be
traced back to the will as a source of desire in the animal. But again, to
claim the source and end of the desire are really one is to face a
contradiction, so one can conclude there is necessarily a distinction in the
animal between the part that moves and the part that is moved.
So
then what can one say about projectile motion? Once a ball takes flight and
leaves the hand, it seems that it continues to move due to no power but its
own. It is clear at least that the person throwing is no longer keeping it in
motion. For one, the person cannot affect or change the motion with his will
the way he could clearly begin the motion with his will. One also knows from
experience that the thrower could be destroyed and the mobile would still
continue in its movement. It is very hard to know what is actually moving the
projectile once it has left its source of motion. Building upon the modern
understanding of this motion as a state named
inertia, Einstein has a per se causal theory that involves the idea of the
projectile body pushing the space in front of it out of the way, which in turn
continues to propel the body through the air. This is a notion that says that bodies don’t need a first
mover because a part (ball) and a part (space) can just move each other over
and over.
However, it is not
necessary to know the per se cause of the continuance of the body through the
air to know that in this motion, too, there must be a first mover. The same
principles of act and potency that say that all motions must have a mover and
that this mover must be some other mover are enough to defend Thomas’ proof. One
must first see that a projectile in motion is in a state contrary to its natural
state. Somehow it has been moved into the air and continues to stay there even when
it naturally abides on the ground, tending towards the center of the earth. Therefore
all projectile motions need a projector, just as other motions need their
acting movers. Now, one may hold that this phenomenon of the ball flying
through the air is the semi-natural state
of inertia rather than the imperfect act
of motion. This allows for the argument that if the body can be coaxed into
having this state, then it is moving of its own power, just as analogously it
could be resting of its own power. Thus one may say that it only stops moving
when something impedes it, and an account of an outside mover/impeder only
needs to be given after the motion is slowed or stopped. But even if motion is
a state of the body, it needs a projector to bring it into that state, and this
projection is not caused by the body itself.
In speaking of
motion as a state, objectors are actually denying that inertial motion is true
motion. For a change in the movement necessitates a cause extrinsic to the
ball, like an impeding wall or acceleration from the wind. And objectors and
Thomists would mostly agree at least on this. Objectors would differ in regards
to simple inertial motion in saying that it does not need any outside cause.
But to say it does not need an extrinsic cause is to say it is not a motion. To
reiterate, that is because motion requires both a potency to act and an
actualization of the potency, and potency cannot actualize itself, so motion is
essentially dependant upon an outside source to do the actualizing. Objectors
acknowledge that all motions need a mover, because they say if inertia does not
need a mover, then it is not a motion, and therefore it must be something
contrary to motion - a state. So even this objection points to the universal
understanding that everything that moves needs a mover. It seems that objectors
might think of the mover more abstractly, though, because ‘mover’ implies
foresight of the end more than a term like ‘cause.’ But at the very least
almost all would agree every motion needs a cause.
It
should be noted in regards to those who hold that inertia undermines Thomas’
first way, that Thomas is not dealing simply in terms of the contained physical
world and energy within the world that modern physics is limited to. Thomas
concludes that there is a first mover, and when he says that this first mover
is put in motion by no other, he is transcending the physical realm of to speak
of its cause. If, as he argues, there can be no infinite chain of (per se) movers,
then there must be a first mover put in motion by no other. And the first mover
must be actual (not in potency), but not with the actuality of moving, rather,
it itself must remain unchanged and non-moving. For if it was moving, it in its
own turn would need a mover, but the premise is that it is the original motion.
Even though Thomas begins from the materially observable phenomenon of motion,
if the first mover must remain unchanged then it must transcend the physical
world, because everything tied to matter changes.
Thomas is giving
an account of the true being of motion that says it is essentially reactive and
dependant on a separate mover, while the theory of inertia is a description of the phenomenon of bodies
moving in space and time. If objectors view inertia as an aspect of the
principle that the physical world’s changes always need a cause (even if they
don’t see inertial motion as one of those changes), then this view is actually
compatible with the account of the being of motion as essentially dependant.
This, then, seems to be a principle of Thomas’ argument that is quickly
understood and easily supposed by all, and perhaps that is why Thomas dubs his
first way ‘the most manifest.’
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