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Question: 78 [<< | >>]
We next treat of the powers of the soul specifically. The theologian,
however, has only to inquire specifically concerning the intellectual and
appetitive powers, in which the virtues reside. And since the knowledge
of these powers depends to a certain extent on the other powers, our
consideration of the powers of the soul taken specifically will be
divided into three parts: first, we shall consider those powers which are
a preamble to the intellect; secondly, the intellectual powers; thirdly,
the appetitive powers.
Under the first head there are four points of inquiry:
(1) The powers of the soul considered generally;
(2) The various species of the vegetative part;
(3) The exterior senses;
(4) The interior senses.
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Question: 78 [<< | >>]
Article: 1 [<< | >>]
Objection 1: It would seem that there are not to be distinguished five genera
of powers in the soul---namely, vegetative, sensitive, appetitive,
locomotive, and intellectual. For the powers of the soul are called its
parts. But only three parts of the soul are commonly assigned---namely,
the vegetative soul, the sensitive soul, and the rational soul. Therefore
there are only three genera of powers in the soul, and not five.
Objection 2: Further, the powers of the soul are the principles of its vital
operations. Now, in four ways is a thing said to live. For the
Philosopher says (De Anima ii, 2): "In several ways a thing is said to
live, and even if only one of these is present, the thing is said to
live; as intellect and sense, local movement and rest, and lastly,
movement of decrease and increase due to nourishment." Therefore there
are only four genera of powers of the soul, as the appetitive is excluded.
Objection 3: Further, a special kind of soul ought not to be assigned as
regards what is common to all the powers. Now desire is common to each
power of the soul. For sight desires an appropriate visible object;
whence we read (Ecclus. 40:22): "The eye desireth favor and beauty, but
more than these green sown fields." In the same way every other power
desires its appropriate object. Therefore the appetitive power should not
be made a special genus of the powers of the soul.
Objection 4: Further, the moving principle in animals is sense, intellect or
appetite, as the Philosopher says (De Anima iii, 10). Therefore the
motive power should not be added to the above as a special genus of soul.
On the contrary, The Philosopher says (De Anima ii, 3), "The powers are
the vegetative, the sensitive, the appetitive, the locomotion, and the
I answer that, There are five genera of powers of the soul, as above
numbered. Of these, three are called souls, and four are called modes of
living. The reason of this diversity lies in the various souls being
distinguished accordingly as the operation of the soul transcends the
operation of the corporeal nature in various ways; for the whole
corporeal nature is subject to the soul, and is related to it as its
matter and instrument. There exists, therefore, an operation of the soul
which so far exceeds the corporeal nature that it is not even performed
by any corporeal organ; and such is the operation of the "rational soul."
Below this, there is another operation of the soul, which is indeed
performed through a corporeal organ, but not through a corporeal quality,
and this is the operation of the "sensitive soul"; for though hot and
cold, wet and dry, and other such corporeal qualities are required for
the work of the senses, yet they are not required in such a way that the
operation of the senses takes place by virtue of such qualities; but only
for the proper disposition of the organ. The lowest of the operations of
the soul is that which is performed by a corporeal organ, and by virtue
of a corporeal quality. Yet this transcends the operation of the
corporeal nature; because the movements of bodies are caused by an
extrinsic principle, while these operations are from an intrinsic
principle; for this is common to all the operations of the soul; since
every animate thing, in some way, moves itself. Such is the operation of
the "vegetative soul"; for digestion, and what follows, is caused
instrumentally by the action of heat, as the Philosopher says (De Anima
Now the powers of the soul are distinguished generically by their
objects. For the higher a power is, the more universal is the object to
which it extends, as we have said above (Question , Article , ad 4). But the
object of the soul's operation may be considered in a triple order. For
in the soul there is a power the object of which is only the body that is
united to that soul; the powers of this genus are called "vegetative" for
the vegetative power acts only on the body to which the soul is united.
There is another genus in the powers of the soul, which genus regards a
more universal object---namely, every sensible body, not only the body to
which the soul is united. And there is yet another genus in the powers of
the soul, which genus regards a still more universal object---namely, not
only the sensible body, but all being in universal. Wherefore it is
evident that the latter two genera of the soul's powers have an operation
in regard not merely to that which is united to them, but also to
something extrinsic. Now, since whatever operates must in some way be
united to the object about which it operates, it follows of necessity
that this something extrinsic, which is the object of the soul's
operation, must be related to the soul in a twofold manner. First,
inasmuch as this something extrinsic has a natural aptitude to be united
to the soul, and to be by its likeness in the soul. In this way there are
two kinds of powers ---namely, the "sensitive" in regard to the less
common object---the sensible body; and the "intellectual," in regard to
the most common object---universal being. Secondly, forasmuch as the soul
itself has an inclination and tendency to the something extrinsic. And in
this way there are again two kinds of powers in the soul: one---the
"appetitive"---in respect of which the soul is referred to something
extrinsic as to an end, which is first in the intention; the other---the
"locomotive" power---in respect of which the soul is referred to
something extrinsic as to the term of its operation and movement; for
every animal is moved for the purpose of realizing its desires and
The modes of living are distinguished according to the degrees of living
things. There are some living things in which there exists only
vegetative power, as the plants. There are others in which with the
vegetative there exists also the sensitive, but not the locomotive power;
such as immovable animals, as shellfish. There are others which besides
this have locomotive powers, as perfect animals, which require many
things for their life, and consequently movement to seek necessaries of
life from a distance. And there are some living things which with these
have intellectual power---namely, men. But the appetitive power does not
constitute a degree of living things; because wherever there is sense
there is also appetite (De Anima ii, 3).
Thus the first two objectives are hereby solved.
Reply to Objection 3: The "natural appetite" is that inclination which each thing
has, of its own nature, for something; wherefore by its natural appetite
each power desires something suitable to itself. But the "animal
appetite" results from the form apprehended; this sort of appetite
requires a special power of the soul---mere apprehension does not
suffice. For a thing is desired as it exists in its own nature, whereas
in the apprehensive power it exists not according to its own nature, but
according to its likeness. Whence it is clear that sight desires
naturally a visible object for the purpose of its act only---namely, for
the purpose of seeing; but the animal by the appetitive power desires the
thing seen, not merely for the purpose of seeing it, but also for other
purposes. But if the soul did not require things perceived by the senses,
except on account of the actions of the senses, that is, for the purpose
of sensing them; there would be no need for a special genus of appetitive
powers, since the natural appetite of the powers would suffice.
Reply to Objection 4: Although sense and appetite are principles of movement in perfect animals, yet sense and appetite, as such, are not sufficient to cause movement, unless another power be added to them; for immovable animals have sense and appetite, and yet they have not the power of motion. Now this motive power is not only in the appetite and sense as commanding the movement, but also in the parts of the body, to make them obey the appetite of the soul which moves them. Of this we have a sign in the fact that when the members are deprived of their natural disposition, they do not move in obedience to the appetite.
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Question: 78 [<< | >>]
Article: 2 [<< | >>]
Objection 1: It would seem that the parts of the vegetative soul are not
fittingly described---namely, the nutritive, augmentative, and
generative. For these are called "natural" forces. But the powers of the
soul are above the natural forces. Therefore we should not class the
above forces as powers of the soul.
Objection 2: Further, we should not assign a particular power of the soul to
that which is common to living and non-living things. But generation is
common to all things that can be generated and corrupted, whether living
or not living. Therefore the generative force should not be classed as a
power of the soul.
Objection 3: Further, the soul is more powerful than the body. But the body by
the same force gives species and quantity; much more, therefore, does the
soul. Therefore the augmentative power of the soul is not distinct from
the generative power.
Objection 4: Further, everything is preserved in being by that whereby it
exists. But the generative power is that whereby a living thing exists.
Therefore by the same power the living thing is preserved. Now the
nutritive force is directed to the preservation of the living thing (De
Anima ii, 4), being "a power which is capable of preserving whatever
receives it." Therefore we should not distinguish the nutritive power
from the generative.
On the contrary, The Philosopher says (De Anima ii, 2,4) that the
operations of this soul are "generation, the use of food," and (cf. De
Anima iii, 9) "growth."
I answer that, The vegetative part has three powers. For the vegetative
part, as we have said (Article ), has for its object the body itself, living
by the soul; for which body a triple operation of the soul is required.
One is whereby it acquires existence, and to this is directed the
"generative" power. Another is whereby the living body acquires its due
quantity; to this is directed the "augmentative" power. Another is
whereby the body of a living thing is preserved in its existence and in
its due quantity; to this is directed the "nutritive" power.
We must, however, observe a difference among these powers. The nutritive
and the augmentative have their effect where they exist, since the body
itself united to the soul grows and is preserved by the augmentative and
nutritive powers which exist in one and the same soul. But the generative
power has its effect, not in one and the same body but in another; for a
thing cannot generate itself. Therefore the generative power, in a way,
approaches to the dignity of the sensitive soul, which has an operation
extending to extrinsic things, although in a more excellent and more
universal manner; for that which is highest in an inferior nature
approaches to that which is lowest in the higher nature, as is made clear
by Dionysius (Div. Nom. vii). Therefore, of these three powers, the
generative has the greater finality, nobility, and perfection, as the
Philosopher says (De Anima ii, 4), for it belongs to a thing which is
already perfect to "produce another like unto itself." And the generative
power is served by the augmentative and nutritive powers; and the
augmentative power by the nutritive.
Reply to Objection 1: Such forces are called natural, both because they produce
an effect like that of nature, which also gives existence, quantity and
preservation (although the above forces accomplish these things in a more
perfect way); and because those forces perform their actions
instrumentally, through the active and passive qualities, which are the
principles of natural actions.
Reply to Objection 2: Generation of inanimate things is entirely from an
extrinsic source; whereas the generation of living things is in a higher
way, through something in the living thing itself, which is the semen
containing the principle productive of the body. Therefore there must be
in the living thing a power that prepares this semen; and this is the
Reply to Objection 3: Since the generation of living things is from a semen, it
is necessary that in the beginning an animal of small size be generated.
For this reason it must have a power in the soul, whereby it is brought
to its appropriate size. But the inanimate body is generated from
determinate matter by an extrinsic agent; therefore it receives at once
its nature and its quantity, according to the condition of the matter.
Reply to Objection 4: As we have said above (Article ), the operation of the
vegetative principle is performed by means of heat, the property of which
is to consume humidity. Therefore, in order to restore the humidity thus
lost, the nutritive power is required, whereby the food is changed into
the substance of the body. This is also necessary for the action of the
augmentative and generative powers.
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Question: 78 [<< | >>]
Article: 3 [<< | >>]
Objection 1: It would seem inaccurate to distinguish five exterior senses. But
there are many kinds of accidents. Therefore, as powers are distinguished
by their objects, it seems that the senses are multiplied according to
the number of the kinds of accidents.
Objection 2: Further, magnitude and shape, and other things which are called
"common sensibles," are "not sensibles by accident," but are
contradistinguished from them by the Philosopher (De Anima ii, 6). Now
the diversity of objects, as such, diversifies the powers. Since,
therefore, magnitude and shape are further from color than sound is, it
seems that there is much more need for another sensitive power than can
grasp magnitude or shape than for that which grasps color or sound.
Objection 3: Further, one sense regards one contrariety; as sight regards
white and black. But the sense of touch grasps several contraries; such
as hot or cold, damp or dry, and suchlike. Therefore it is not a single
sense but several. Therefore there are more than five senses.
Objection 4: Further, a species is not divided against its genus. But taste is
a kind of touch. Therefore it should not be classed as a distinct sense
On the contrary, The Philosopher says (De Anima iii, 1): "There is no
other besides the five senses."
I answer that, The reason of the distinction and number of the senses
has been assigned by some to the organs in which one or other of the
elements preponderate, as water, air, or the like. By others it has been
assigned to the medium, which is either in conjunction or extrinsic and
is either water or air, or such like. Others have ascribed it to the
various natures of the sensible qualities, according as such quality
belongs to a simple body or results from complexity. But none of these
explanations is apt. For the powers are not for the organs, but the
organs for the powers; wherefore there are not various powers for the
reason that there are various organs; on the contrary, for this has
nature provided a variety of organs, that they might be adapted to
various powers. In the same way nature provided various mediums for the
various senses, according to the convenience of the acts of the powers.
And to be cognizant of the natures of sensible qualities does not pertain
to the senses, but to the intellect.
The reason of the number and distinction of the exterior senses must
therefore be ascribed to that which belongs to the senses properly and
"per se." Now, sense is a passive power, and is naturally immuted by the
exterior sensible. Wherefore the exterior cause of such immutation is
what is "per se" perceived by the sense, and according to the diversity
of that exterior cause are the sensitive powers diversified.
Now, immutation is of two kinds, one natural, the other spiritual.
Natural immutation takes place by the form of the immuter being received
according to its natural existence, into the thing immuted, as heat is
received into the thing heated. Whereas spiritual immutation takes place
by the form of the immuter being received, according to a spiritual mode
of existence, into the thing immuted, as the form of color is received
into the pupil which does not thereby become colored. Now, for the
operation of the senses, a spiritual immutation is required, whereby an
intention of the sensible form is effected in the sensile organ.
Otherwise, if a natural immutation alone sufficed for the sense's action,
all natural bodies would feel when they undergo alteration.
But in some senses we find spiritual immutation only, as in "sight"
while in others we find not only spiritual but also a natural immutation;
either on the part of the object only, or likewise on the part of the
organ. On the part of the object we find natural immutation, as to
place, in sound which is the object of "hearing"; for sound is caused by
percussion and commotion of air: and we find natural immutation by
alteration, in odor which is the object of "smelling"; for in order to
exhale an odor, a body must be in a measure affected by heat. On the part
of an organ, natural immutation takes place in "touch" and "taste"; for
the hand that touches something hot becomes hot, while the tongue is
moistened by the humidity of the flavored morsel. But the organs of
smelling and hearing are not affected in their respective operations by
any natural immutation unless indirectly.
Now, the sight, which is without natural immutation either in its organ
or in its object, is the most spiritual, the most perfect, and the most
universal of all the senses. After this comes the hearing and then the
smell, which require a natural immutation on the part of the object;
while local motion is more perfect than, and naturally prior to, the
motion of alteration, as the Philosopher proves (Phys. viii, 7). Touch
and taste are the most material of all: of the distinction of which we
shall speak later on (ad 3,4). Hence it is that the three other senses
are not exercised through a medium united to them, to obviate any natural
immutation in their organ; as happens as regards these two senses.
Reply to Objection 1: Not every accident has in itself a power of immutation but
only qualities of the third species, which are the principles of
alteration: therefore only suchlike qualities are the objects of the
senses; because "the senses are affected by the same things whereby
inanimate bodies are affected," as stated in Phys. vii, 2.
Reply to Objection 2: Size, shape, and the like, which are called "common
sensibles," are midway between "accidental sensibles" and "proper
sensibles," which are the objects of the senses. For the proper sensibles
first, and of their very nature, affect the senses; since they are
qualities that cause alteration. But the common sensibles are all
reducible to quantity. As to size and number, it is clear that they are
species of quantity. Shape is a quality about quantity. Shape is a
quality about quantity, since the notion of shape consists of fixing the
bounds of magnitude. Movement and rest are sensed according as the
subject is affected in one or more ways in the magnitude of the subject
or of its local distance, as in the movement of growth or of locomotion,
or again, according as it is affected in some sensible qualities, as in
the movement of alteration; and thus to sense movement and rest is, in a
way, to sense one thing and many. Now quantity is the proximate subject
of the qualities that cause alteration, as surface is of color. Therefore
the common sensibles do not move the senses first and of their own
nature, but by reason of the sensible quality; as the surface by reason
of color. Yet they are not accidental sensibles, for they produce a
certain variety in the immutation of the senses. For sense is immuted
differently by a large and by a small surface: since whiteness itself is
said to be great or small, and therefore it is divided according to its
Reply to Objection 3: As the Philosopher seems to say (De Anima ii, 11), the
sense of touch is generically one, but is divided into several specific
senses, and for this reason it extends to various contrarieties; which
senses, however, are not separate from one another in their organ, but
are spread throughout the whole body, so that their distinction is not
evident. But taste, which perceives the sweet and the bitter, accompanies
touch in the tongue, but not in the whole body; so it is easily
distinguished from touch. We might also say that all those contrarieties
agree, each in some proximate genus, and all in a common genus, which is
the common and formal object of touch. Such common genus is, however,
unnamed, just as the proximate genus of hot and cold is unnamed.
Reply to Objection 4: The sense of taste, according to a saying of the
Philosopher (De Anima ii, 9), is a kind of touch existing in the tongue
only. It is not distinct from touch in general, but only from the species
of touch distributed in the body. But if touch is one sense only, on
account of the common formality of its object: we must say that taste is
distinguished from touch by reason of a different formality of
immutation. For touch involves a natural, and not only a spiritual,
immutation in its organ, by reason of the quality which is its proper
object. But the organ of taste is not necessarily immuted by a natural
immutation by reason of the quality which is its proper object, so that
the tongue itself becomes sweet and bitter: but by reason of a quality
which is a preamble to, and on which is based, the flavor, which quality
is moisture, the object of touch.
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First Part [<< | >>]
Question: 78 [<< | >>]
Article: 4 [<< | >>]
Objection 1: It would seem that the interior senses are not suitably
distinguished. For the common is not divided against the proper.
Therefore the common sense should not be numbered among the interior
sensitive powers, in addition to the proper exterior senses.
Objection 2: Further, there is no need to assign an interior power of
apprehension when the proper and exterior sense suffices. But the proper
and exterior senses suffice for us to judge of sensible things; for each
sense judges of its proper object. In like manner they seem to suffice
for the perception of their own actions; for since the action of the
sense is, in a way, between the power and its object, it seems that sight
must be much more able to perceive its own vision, as being nearer to it,
than the color; and in like manner with the other senses. Therefore for
this there is no need to assign an interior power, called the common
Objection 3: Further, according to the Philosopher (De Memor. et Remin. i), the imagination and the memory are passions of the "first sensitive." But passion is not divided against its subject. Therefore memory and imagination should not be assigned as powers distinct from the senses.
Objection 4: Further, the intellect depends on the senses less than any power
of the sensitive part. But the intellect knows nothing but what it
receives from the senses; whence we read (Poster. i, 8), that "those who
lack one sense lack one kind of knowledge." Therefore much less should we
assign to the sensitive part a power, which they call the "estimative"
power, for the perception of intentions which the sense does not perceive.
Objection 5: Further, the action of the cogitative power, which consists in
comparing, adding and dividing, and the action of the reminiscence, which
consists in the use of a kind of syllogism for the sake of inquiry, is
not less distant from the actions of the estimative and memorative
powers, than the action of the estimative is from the action of the
imagination. Therefore either we must add the cognitive and reminiscitive
to the estimative and memorative powers, or the estimative and memorative
powers should not be made distinct from the imagination.
Objection 6: Further, Augustine (Gen. ad lit. xii, 6,7,24) describes three
kinds of vision; namely, corporeal, which is the action of the sense;
spiritual, which is an action of the imagination or phantasy; and
intellectual, which is an action of the intellect. Therefore there is no
interior power between the sense and intellect, besides the imagination.
On the contrary, Avicenna (De Anima iv, 1) assigns five interior
sensitive powers; namely, "common sense, phantasy, imagination, and the
estimative and memorative powers."
I answer that, As nature does not fail in necessary things, there must
needs be as many actions of the sensitive soul as may suffice for the
life of a perfect animal. If any of these actions cannot be reduced to
the same one principle, they must be assigned to diverse powers; since a
power of the soul is nothing else than the proximate principle of the
Now we must observe that for the life of a perfect animal, the animal
should apprehend a thing not only at the actual time of sensation, but
also when it is absent. Otherwise, since animal motion and action follow
apprehension, an animal would not be moved to seek something absent: the
contrary of which we may observe specially in perfect animals, which are
moved by progression, for they are moved towards something apprehended
and absent. Therefore an animal through the sensitive soul must not only
receive the species of sensible things, when it is actually affected by
them, but it must also retain and preserve them. Now to receive and
retain are, in corporeal things, reduced to diverse principles; for moist
things are apt to receive, but retain with difficulty, while it is the
reverse with dry things. Wherefore, since the sensitive power is the act
of a corporeal organ, it follows that the power which receives the
species of sensible things must be distinct from the power which
Again we must observe that if an animal were moved by pleasing and
disagreeable things only as affecting the sense, there would be no need
to suppose that an animal has a power besides the apprehension of those
forms which the senses perceive, and in which the animal takes pleasure,
or from which it shrinks with horror. But the animal needs to seek or to
avoid certain things, not only because they are pleasing or otherwise to
the senses, but also on account of other advantages and uses, or
disadvantages: just as the sheep runs away when it sees a wolf, not on
account of its color or shape, but as a natural enemy: and again a bird
gathers together straws, not because they are pleasant to the sense, but
because they are useful for building its nest. Animals, therefore, need
to perceive such intentions, which the exterior sense does not perceive.
And some distinct principle is necessary for this; since the perception
of sensible forms comes by an immutation caused by the sensible, which is
not the case with the perception of those intentions.
Thus, therefore, for the reception of sensible forms, the "proper sense"
and the "common sense" are appointed, and of their distinction we shall
speak farther on (ad 1,2). But for the retention and preservation of
these forms, the "phantasy" or "imagination" is appointed; which are the
same, for phantasy or imagination is as it were a storehouse of forms
received through the senses. Furthermore, for the apprehension of
intentions which are not received through the senses, the "estimative"
power is appointed: and for the preservation thereof, the "memorative"
power, which is a storehouse of such-like intentions. A sign of which we
have in the fact that the principle of memory in animals is found in some
such intention, for instance, that something is harmful or otherwise. And
the very formality of the past, which memory observes, is to be reckoned
among these intentions.
Now, we must observe that as to sensible forms there is no difference
between man and other animals; for they are similarly immuted by the
extrinsic sensible. But there is a difference as to the above intentions:
for other animals perceive these intentions only by some natural
instinct, while man perceives them by means of coalition of ideas.
Therefore the power by which in other animals is called the natural
estimative, in man is called the "cogitative," which by some sort of
collation discovers these intentions. Wherefore it is also called the
"particular reason," to which medical men assign a certain particular
organ, namely, the middle part of the head: for it compares individual
intentions, just as the intellectual reason compares universal
intentions. As to the memorative power, man has not only memory, as other
animals have in the sudden recollection of the past; but also
"reminiscence" by syllogistically, as it were, seeking for a recollection
of the past by the application of individual intentions. Avicenna,
however, assigns between the estimative and the imaginative, a fifth
power, which combines and divides imaginary forms: as when from the
imaginary form of gold, and imaginary form of a mountain, we compose the
one form of a golden mountain, which we have never seen. But this
operation is not to be found in animals other than man, in whom the
imaginative power suffices thereto. To man also does Averroes attribute
this action in his book De sensu et sensibilibus (viii). So there is no
need to assign more than four interior powers of the sensitive
part---namely, the common sense, the imagination, and the estimative and
Reply to Objection 1: The interior sense is called "common" not by predication,
as if it were a genus; but as the common root and principle of the
Reply to Objection 2: The proper sense judges of the proper sensible by
discerning it from other things which come under the same sense; for
instance, by discerning white from black or green. But neither sight nor
taste can discern white from sweet: because what discerns between two
things must know both. Wherefore the discerning judgment must be assigned
to the common sense; to which, as to a common term, all apprehensions of
the senses must be referred: and by which, again, all the intentions of
the senses are perceived; as when someone sees that he sees. For this
cannot be done by the proper sense, which only knows the form of the
sensible by which it is immuted, in which immutation the action of sight
is completed, and from immutation follows another in the common sense
which perceives the act of vision.
Reply to Objection 3: As one power arises from the soul by means of another, as
we have seen above (Question , Article ), so also the soul is the subject of one
power through another. In this way the imagination and the memory are
called passions of the "first sensitive."
Reply to Objection 4: Although the operation of the intellect has its origin in
the senses: yet, in the thing apprehended through the senses, the
intellect knows many things which the senses cannot perceive. In like
manner does the estimative power, though in a less perfect manner.
Reply to Objection 5: The cogitative and memorative powers in man owe their
excellence not to that which is proper to the sensitive part; but to a
certain affinity and proximity to the universal reason, which, so to
speak, overflows into them. Therefore they are not distinct powers, but
the same, yet more perfect than in other animals.
Reply to Objection 6: Augustine calls that vision spiritual which is effected by
the images of bodies in the absence of bodies. Whence it is clear that it
is common to all interior apprehensions.