Why
does the human soul persist after death whereas the souls of animals
do not? In order to answer these questions clearly, we must first
define what a soul is and then explore the difference between human
and animal souls. To form the basis for our inquiry, we will first
prove that all living things have immaterial souls that are distinct
from their material bodies and that there are different kinds of
souls for the different kinds of living things. Once this basis has
been sufficiently laid out, we will focus specifically on whether it
is possible for each kind of soul to continue to exist after death.
Then of course we will determine whether it is possible for the soul
not to exist after death, and by this come to our conclusion that the
human soul does indeed persist after bodily death, whereas the souls
of animals are destroyed.
We
begin with our first question, “what is a soul?” We say that a
thing has a soul insofar as it is alive. Life is manifested
primarily as nutrition and growth by which something is moved by an
intrinsic principle. This power is proper to all living things and
is the fullest extent of life in what are called nutritive or
vegetative souls (such as plants). In animals, life is also
manifested in sensation and directive movement, which is why their
souls are called sensitive souls. These two demarcations, vegetative
and sensible, are enough to identify three ways in which the soul can
be understood in relation to a living thing; viz. as form, as mover
(or intrinsic efficient cause), and as end (or final cause).
Aristotle
identifies the soul as the form
of a living body, which is to say that the soul is what makes a
living body what it is. This is not merely a definition of life,
that a soul is merely what it means
to be alive. Rather, the soul subsists as the actuality
of a living body.1
This means that what is potentially alive is made actually alive by
its soul. This also accounts for the integrity of individual living
things, as the form is what gives the material elements of a thing
the status of parts of a whole.2
With regard to motion,
Aristotle identifies desire as the primary principle of motion and
attributes this to sensible souls.3
There is also motion in the sense of nutrition and growth in
vegetative souls and, for our present purpose, it is enough to
mention that vegetative souls, while possessing neither a desire
prompted by the senses nor the deliberation of reason, they are still
inclined to motion with respect to nutrition and growth.
Thus all living things are moved internally by a function or part of
their souls. With regard to the end,
Aristotle identifies the primary end of a living thing as the soul
itself.4
This is simply to say that the goal of all living things is to live.
Because such things are body-soul composites, they are bound to
corruption and death. Hence in order to attain the end of life (no
pun intended) they are generative, producing things like themselves
in species, thereby continuing life specifically, though individually
it dies. This necessitates a body in order for subsistence and
generation to take place, albeit the body is in this regard a means
to the end.5
By
acknowledging these three roles, it might seem that the soul is some
emergent property or function of material arising out of a material
cause. We will consider four arguments which support this. Firstly,
if the soul is the form of the
body, then the soul only exists insofar as it informs the body.
Therefore, it is reasonable to infer that the soul is something
dependent on the body.6
Secondly, if souls are identified according to their activity
(as a vegetative soul vegetates and a sensible soul senses) then we
ought to consider them precisely to be activities and nothing more.
For what we observe in living things are not souls as such, but
vegetation and sensation, by which we infer that there is something
other than what we observe which performs those activities. But this
is an unnecessary abstraction, as we perceive nothing other than
activity in a material body.7
Thirdly, if
the soul is the principle of movement in material things, then it
interacts with material. But what is immaterial is impassible and
cannot interact with what is material. Therefore the soul must not
be immaterial but something material. Finally,
the end of a living thing is to preserve its life. But
self-preservation is achieved in and through the preservation of the
body. Therefore, life-as-end is not distinct from the body but is
merely the integrity of the body and its functions.
Against
the first
argument, we should
note that if we regard the form as dependent on matter as a kind of
supervening quality, then we would subvert the order of substance and
accidents. What is accidental to a thing is secondary to what the
thing primarily is, which is its substance. When the soul is called
the form of the body, it is precisely meant as the substantial form.
Even though matter is a necessary part of a natural living thing, the
matter is not enough to identify that thing as what it is, as we see
that a plant or animal can grow and diminish over time while
maintaining its individuality. But to say that a living thing's soul
exists only insofar as it has matter is to put accidents prior to
substance or else make matter the substantial form of the body, which
is absurd. Hence, if we wish to concede that there are individual
living things, then the primacy of the soul is a necessary conclusion
from what is perceived.8
To the second argument, we can build on our first reply. We
ascertain the form of a thing when we identify what it is
specifically (i.e. according to a species), for matter is informed
according to its species by its form. This is not merely a logical
device, for to refer to a substantial form is to say that there is
some active principle in that living thing which unifies the parts
into a whole. Now when we observe some activity in a certain thing,
we can attribute that activity in two ways; to the part in which the
activity is manifested, and to the whole to which the part belongs.
E.g. when a worm is prodded, we may say that there is a reaction in
certain material parts of that worm, and that what we observe is the
action of material apparata in response to some material stimulus.
This may be true with respect to chemistry, but it is ultimately
unintelligible without respect to the thing acting, viz. the worm.
If we cannot account for the substantial form of the worm, then we
cannot say that the worm moves, but only that the parts of the worm
move. But this is an unnecessary reduction, whereas it is reasonable
to attribute the movement observed within a thing to the thing
itself.
To the third argument, it would indeed seem that immaterial things
cannot interact with material for two reasons; viz. that what is
material cannot harm or hinder what is immaterial (e.g. we cannot tie
down an angel or transplant a soul) and that there is no known
mechanism which would explain how such an interaction could take
place. But we should not form too simple a concept of immaterial
things. Some tend to think of interaction in terms of bodies
responding to touch, like two rocks hitting together. But no
interaction at all can be attributed to purely material causes. The
rocks that one knocks together are being moved ultimately by
something that does the moving. So the answer to the question, how
does the immaterial interact with the material, is found in the
question, “what is interaction?” Strictly speaking, “pure
matter” does not act. To hold this would ultimately be to conflate
material cause and efficient cause and to disregard the act-potency
distinction altogether. Therefore we must concede that there is
something immaterial in a living thing which is the principle of its
action.
In response to the fourth argument, it should suffice to say that,
having proved the existence of the soul as the substantial form of a
living thing, the body is the matter which is informed by the soul,
and through such the soul acts. Thus the integrity of the body is
due to the soul's act, which works in and through the body as the
means to preserve its proper place as form. Because preservation of
life is attained through the body, it does not follow that the life
of the body is the body itself.
It
should now be clear what the soul is; the substantial form of a
living being, as well as its active principle, accounting for its
growth and sensation, with the end of subsisting itself and in
generating life according to its same species. This account of the
soul suffices for all animals except man, whose soul is rational in
addition to the aforementioned qualities. As mentioned above, the
soul (as form) informs matter to participate in a given species.
According to Aristotle, a species is nothing other than some member
of a genus which is distinguished by means of some difference.9
The essence of man is the composite of his form and (indeterminate)
matter and is expressed by its definition.10
This means that the definition of man is precisely a description of
his differentiation as a species within his genus. Hence we define
man as “rational animal,” in the genus “animal” and
differentiated from other animals by his rational intellect. This
leaves us with three kinds of souls altogether; vegetative, sensible,
and man's, which is called the rational soul.
As
we have said, the difference between a man's soul and an animal's
soul is in the intellect. So if there is a difference between
sensible and rational souls in their ability to survive death, then
it must be on account of the intellect. But whether the sensible
soul can survive death is still to be determined. In order to
understand how the material destruction of a thing can effect its
substantial form, it is helpful to understand that there is a kind of
hierarchy of forms, owing to their relation to the matter in which
they act, as St. Thomas says:
[I]t must be considered that a
gradation of forms in the order of operation corresponds to the
gradation of forms in the order of existence, for an operation is an
act of an agent in act. Therefore the greater perfection a form
possesses with respect to conferring the act of existing, so much the
greater is its power of operating. Hence more perfect forms have a
greater number of operations and more diverse ones than less perfect
forms (DA 9 resp.).11
Thus
we have varying levels of forms corresponding to different levels of
perfection; material forms (such as the form of bronze), the forms of
living things, the forms of sensible animals, and the rational form
found in human beings.12
So we should note that an animal has perfections according to their
material being, their being alive, and their being an animal, and a
man specifically has one more perfection, that of being rational.
That
a being has several formal perfections does not necessitate its
having several souls. As explained above, the soul is a substantial
form. There can only be one substantial form of any given thing, as
the substantial form is precisely what accounts for its being a
substance. And a substance is something which is adjoined by
accidents, the latter existing in a thing by virtue of the former (we
can see an analogous relation between a predicate and its subject).
But a (primary) substance cannot be predicated of another substance.
So if an individual were to have many souls, he would necessarily be
a conglomeration of many substances and hence would not be an
individual at all, which is absurd.13
It
should now be clear that there is a “gradation of forms in the
order of operation” in living things, not on account of an
accumulation of various forms, but on account of a gradation of power
according to each form. For example, the sensible soul is superior
to material forms, for the sensible soul not only informs matter but
grows and perceives as well. And the rational soul is superior to
the sensible, because the rational is able to conceive of immaterial
things in the intellect, and this in addition to the powers proper to
the sensible soul.
So, having given a precise account of sensible and rational souls as
well as their differences, we can now explain why sensible souls
cannot survive death. St. Thomas explains this in the following:
[T]hings composed of matter and
form are corrupted by losing the form that gives them their act of
existing. Moreover a form itself cannot be corrupted in itself (per
se), but is corrupted
accidentally as a result of the disintegration of the composite,
inasmuch as the composite, which exists in virtue of its form, ceases
to exist as a composite. This indeed, is the case if the form is one
that does not have an act of existing in itself, but is merely that
by which a composite exists.14
Thomas
here distinguishes between a form which is the act of existing in a
composite (form and matter) and a form which is its own act of
existing. We can see how this plays into the question of death by
resuscitating our first and fourth objections from above and adding
some qualifications. If a certain soul exists only
as that which informs some matter, then the soul only exists insofar
as it informs the body. Therefore it is necessary that the soul is
something dependent on the body, not as an emergent property but in
regards to its subsistence. Such a soul subsists in composition with
its matter by preserving the integrity of the composite in the matter
through which it operates. Thus the disintegration of the composite
in death entails the dissolution of that soul which formed the
composite. Simply put, the soul of a dog informs some matter as a
dog's matter. Everything the dog's soul does is done through in its
matter. If you disintegrate the dog then its soul ceases to exist
because there is nothing left for there to be a dog.
As noted above, the human soul
differs from other animals in his intellect. Man exists as an animal
by means of his body, but rationally by means of his intellect.
Thomas explains:
Now if there is a form having an
act of existing in itself, then that form must be incorruptible. For
a thing having an act of existing (esse)
does not cease to exist unless its form is separated from it. Hence
if the thing having an act of existing is itself a form, it is
impossible for its act of existing to be separated from it. Now it is
evident that the principle by which a man understands is a form
having its act of existing in itself and is not merely that by which
something exists. For, as the Philosopher proves in the De
anima
[III, 4, 429b 3], intellection is not an act executed by any bodily
organ.15
While
man's soul shares with other animals the operations proper to their
bodies, the operation of his soul in the intellect is distinct from
his body. Though man acquires knowledge beginning with the
perception of material things by means of his body, all three causes
present in his soul (formal, efficient, and final) act in the
intellect without the incorporation of matter. His intellect does
not exist as any material thing. His act of intellection moves by an
intrinsic principle, without material cooperation. And the end of
his intellect is not merely the preservation of life, but the
attainment of truth, which is ultimately not attained in nor
attributable to his matter. Thus we can see that the rational soul
does not exist by virtue of its composition with matter, but exists
in its own right. Therefore when man's body dies, his soul must
survive.16
1 Aristotle,
De Anima in Introductory Readings in Ancient Greek and Roman
Philosophy, eds. Reeve and Miller (Indianapolis: Hackett, 2006),
278.
2 ibid.
3 Aristotle,
De Anima, 285.
4 Op.
cit. 281.
5 Op.
cit. 282.
6 Thomas
Aquinas, Quaestiones Disputate De Anima,
trans. John Patrick Rowan (St. Louis: B. Herder Book Co., 1949), A
14, Obj. 1
7 Op.
cit. A 12, Obj. 2
8 Thomas
Aquinas, Summa Contra Gentiles,
ed. Joseph Kenny (NY: Hanover House, 1957), II.xxvi.3
9 Aristotle,
Metaphysics, trans. Joe
Sachs (Santa Fe: Green Lion Press, 1999), 998b (pg. 43).
10 Thomas
Aquinas, De Ente et Essentia, trans. Armand Maurer (Toronto:
Pontifical Institute of Mediaeval Studies, 1968), IV.iii (pg. 36).
11 Aquinas,
De Anima, 9 resp.
12 ibid.
13 Aquinas,
De Anima, 11 resp..
14 Op.
cit. 14 resp.
15 ibid.
16 ibid.