QUESTION 115: OF THE ACTION OF THE CORPOREAL CREATURE
We have now to consider the action of the corporeal creature; and fate,
which is ascribed to certain bodies. Concerning corporeal actions there
are six points of inquiry:
(1) Whether a body can be active?
(2) Whether there exist in bodies certain seminal virtues?
(3) Whether the heavenly bodies are the causes of what is done here by
the inferior bodies?
(4) Whether they are the cause of human acts?
(5) Whether demons are subject to their influence?
(6) Whether the heavenly bodies impose necessity on those things which
are subject to their influence?
Article 1: Whether a body can be active?
Objection 1: It would seem that no bodies are active. For Augustine says (De
Civ. Dei v, 9): "There are things that are acted upon, but do not act;
such are bodies: there is one Who acts but is not acted upon; this is
God: there are things that both act and are acted upon; these are the
Objection 2: Further, every agent except the first agent requires in its work
a subject susceptible of its action. But there is not substance below the
corporeal substance which can be susceptible of the latter's action;
since it belongs to the lowest degree of beings. Therefore corporeal
substance is not active.
Objection 3: Further, every corporeal substance is limited by quantity. But
quantity hinders substance from movement and action, because it surrounds
it and penetrates it: just as a cloud hinders the air from receiving
light. A proof of this is that the more a body increases in quantity, the
heavier it is and the more difficult to move. Therefore no corporeal
substance is active.
Objection 4: Further, the power of action in every agent is according to its
propinquity to the first active cause. But bodies, being most composite,
are most remote from the first active cause, which is most simple.
Therefore no bodies are active.
Objection 5: Further, if a body is an agent, the term of its action is either
a substantial, or an accidental form. But it is not a substantial form;
for it is not possible to find in a body any principle of action, save an
active quality, which is an accident; and an accident cannot be the cause
of a substantial form, since the cause is always more excellent than the
effect. Likewise, neither is it an accidental form, for "an accident does
not extend beyond its subject," as Augustine says (De Trin. ix, 4).
Therefore no bodies are active.
On the contrary, Dionysius says (Coel. Hier. xv) that among other
qualities of corporeal fire, "it shows its greatness in its action and
power on that of which it lays hold."
I answer that, It is apparent to the senses that some bodies are active.
But concerning the action of bodies there have been three errors. For
some denied all action to bodies. This is the opinion of Avicebron in his
book on The Fount of Life, where, by the arguments mentioned above, he
endeavors to prove that no bodies act, but that all the actions which
seem to be the actions of bodies, are the actions of some spiritual power
that penetrates all bodies: so that, according to him, it is not fire
that heats, but a spiritual power which penetrates, by means of the fire.
And this opinion seems to be derived from that of Plato. For Plato held
that all forms existing in corporeal matter are participated thereby, and
determined and limited thereto; and that separate forms are absolute and
as it were universal; wherefore he said that these separate forms are the
causes of forms that exist in matter. Therefore inasmuch as the form
which is in corporeal matter is determined to this matter individualized
by quantity, Avicebron held that the corporeal form is held back and
imprisoned by quantity, as the principle of individuality, so as to be
unable by action to extend to any other matter: and that the spiritual
and immaterial form alone, which is not hedged in by quantity, can issue
forth by acting on something else.
But this does not prove that the corporeal form is not an agent, but
that it is not a universal agent. For in proportion as a thing is
participated, so, of necessity, must that be participated which is proper
thereto; thus in proportion to the participation of light is the
participation of visibility. But to act, which is nothing else than to
make something to be in act, is essentially proper to an act as such;
wherefore every agent produces its like. So therefore to the fact of its
being a form not determined by matter subject to quantity, a thing owes
its being an agent indeterminate and universal: but to the fact that it
is determined to this matter, it owes its being an agent limited and
particular. Wherefore if the form of fire were separate, as the
Platonists supposed, it would be, in a fashion, the cause of every
ignition. But this form of fire which is in this corporeal matter, is the
cause of this ignition which passes from this body to that. Hence such
an action is effected by the contact of two bodies.
But this opinion of Avicebron goes further than that of Plato. For Plato
held only substantial forms to be separate; while he referred accidents
to the material principles which are "the great" and "the small," which
he considered to be the first contraries, by others considered to the
"the rare" and "the dense." Consequently both Plato and Avicenna, who
follows him to a certain extent, held that corporeal agents act through
their accidental forms, by disposing matter for the substantial form; but
that the ultimate perfection attained by the introduction of the
substantial form is due to an immaterial principle. And this is the
second opinion concerning the action of bodies; of which we have spoken
above when treating of the creation (Question , Article ).
The third opinion is that of Democritus, who held that action takes
place through the issue of atoms from the corporeal agent, while passion
consists in the reception of the atoms in the pores of the passive body.
This opinion is disproved by Aristotle (De Gener. i, 8,9). For it would
follow that a body would not be passive as a whole, and the quantity of
the active body would be diminished through its action; which things are
We must therefore say that a body acts forasmuch as it is in act, on a
body forasmuch as it is in potentiality.
Reply to Objection 1: This passage of Augustine is to be understood of the whole
corporeal nature considered as a whole, while thus has no nature inferior
to it, on which it can act; as the spiritual nature acts on the
corporeal, and the uncreated nature on the created. Nevertheless one body
is inferior to another, forasmuch as it is in potentiality to that which
the other has in act.
From this follows the solution of the second objection. But it must be
observed, when Avicebron argues thus, "There is a mover who is not moved,
to wit, the first maker of all; therefore, on the other hand, there
exists something moved which is purely passive," that this is to be
conceded. But this latter is primary matter, which is a pure
potentiality, just as God is pure act. Now a body is composed of
potentiality and act; and therefore it is both active and passive.
Reply to Objection 3: Quantity does not entirely hinder the corporeal form from
action, as stated above; but from being a universal agent, forasmuch as a
form is individualized through being in matter subject to quantity. The
proof taken from the weight of bodies is not to the purpose. First,
because addition of quantity does not cause weight; as is proved (De
Coelo et Mundo iv, 2). Secondly, it is false that weight retards
movement; on the contrary, the heavier a thing, the greater its movement,
if we consider the movement proper thereto. Thirdly, because action is
not effected by local movement, as Democritus held: but by something
being reduced from potentiality to act.
Reply to Objection 4: A body is not that which is most distant from God; for it
participates something of a likeness to the Divine Being, forasmuch as it
has a form. That which is most distant from God is primary matter; which
is in no way active, since it is a pure potentiality.
Reply to Objection 5: The term of a body's action is both an accidental form and
a substantial form. For the active quality, such as heat, although itself
an accident, acts nevertheless by virtue of the substantial form, as its
instrument: wherefore its action can terminate in a substantial form;
thus natural heat, as the instrument of the soul, has an action
terminating in the generation of flesh. But by its own virtue it produces
an accident. Nor is it against the nature of an accident to surpass its
subject in acting, but it is to surpass it in being; unless indeed one
were to imagine that an accident transfers its identical self from the
agent to the patient; thus Democritus explained action by an issue of
Article 2: Whether there are any seminal virtues in corporeal matter?
Objection 1: It would seem that there are no seminal virtues in corporeal
matter. For virtue [ratio] implies something of a spiritual order. But in
corporeal matter nothing exists spiritually, but only materially, that
is, according to the mode of that in which it is. Therefore there are no
seminal virtues in corporeal matter.
Objection 2: Further, Augustine (De Trin. iii, 8,9) says that demons produce
certain results by employing with a hidden movement certain seeds, which
they know to exist in matter. But bodies, not virtues, can be employed
with local movement. Therefore it is unreasonable to say that there are
seminal virtues in corporeal matter.
Objection 3: Further, seeds are active principles. But there are no active
principles in corporeal matter; since, as we have said above, matter is
not competent to act (Article , ad 2,4). Therefore there are no seminal
virtues in corporeal matter.
Objection 4: Further, there are said to be certain "causal virtues"
(Augustine, De Gen. ad lit. v, 4) which seem to suffice for the
production of things. But seminal virtues are not causal virtues: for
miracles are outside the scope of seminal virtues, but not of causal
virtues. Therefore it is unreasonable to say that there are seminal
virtues in corporeal matter.
On the contrary, Augustine says (De Trin. iii, 8): "Of all the things
which are generated in a corporeal and visible fashion, certain seeds lie
hidden in the corporeal things of this world."
I answer that, It is customary to name things after what is more
perfect, as the Philosopher says (De Anima ii, 4). Now in the whole
corporeal nature, living bodies are the most perfect: wherefore the word
"nature" has been transferred from living things to all natural things.
For the word itself, "nature," as the Philosopher says (Metaph. v, Did.
iv, 4), was first applied to signify the generation of living things,
which is called "nativity": and because living things are generated from
a principle united to them, as fruit from a tree, and the offspring from
the mother, to whom it is united, consequently the word "nature" has been
applied to every principle of movement existing in that which is moved.
Now it is manifest that the active and passive principles of the
generation of living things are the seeds from which living things are
generated. Therefore Augustine fittingly gave the name of "seminal
virtues" [seminales rationes] to all those active and passive virtues
which are the principles of natural generation and movement.
These active and passive virtues may be considered in several orders.
For in the first place, as Augustine says (Gen. ad lit. vi, 10), they are
principally and originally in the Word of God, as "typal ideas."
Secondly, they are in the elements of the world, where they were produced
altogether at the beginning, as in "universal causes." Thirdly, they are
in those things which, in the succession of time, are produced by
universal causes, for instance in this plant, and in that animal, as in
"particular causes." Fourthly, they are in the "seeds" produced from
animals and plants. And these again are compared to further particular
effects, as the primordial universal causes to the first effects produced.
Reply to Objection 1: These active and passive virtues of natural things, thought
not called "virtues" [rationes] by reason of their being in corporeal
matter, can nevertheless be so called in respect of their origin,
forasmuch as they are the effect of the typal ideas [rationes ideales].
Reply to Objection 2: These active and passive virtues are in certain parts of
corporeal things: and when they are employed with local movement for the
production of certain results, we speak of the demons as employing seeds.
Reply to Objection 3: The seed of the male is the active principle in the
generation of an animal. But that can be called seed also which the
female contributes as the passive principle. And thus the word "seed"
covers both active and passive principles.
Reply to Objection 4: From the words of Augustine when speaking of these seminal
virtues, it is easy to gather that they are also causal virtues, just as
seed is a kind of cause: for he says (De Trin. iii, 9) that, "as a mother
is pregnant with the unborn offspring, so is the world itself pregnant
with the causes of unborn things." Nevertheless, the "typal ideas" can be
called "causal virtues," but not, strictly speaking, "seminal virtues,"
because seed is not a separate principle; and because miracles are not
wrought outside the scope of causal virtues. Likewise neither are
miracles wrought outside the scope of the passive virtues so implanted in
the creature, that the latter can be used to any purpose that God
commands. But miracles are said to be wrought outside the scope of the
natural active virtues, and the passive potentialities which are ordered
to such active virtues, and this is what is meant when we say that they
are wrought outside the scope of seminal virtues.
Article 3: Whether the heavenly bodies are the cause of what is produced in bodies here below?
Objection 1: It would seem that the heavenly bodies are not the cause of what
is produced in bodies here below. For Damascene says (De Fide Orth. ii,
7): "We say that they"---namely, the heavenly bodies---"are not the cause
of generation or corruption: they are rather signs of storms and
Objection 2: Further, for the production of anything, an agent and matter
suffice. But in things here below there is passive matter; and there are
contrary agents---heat and cold, and the like. Therefore for the
production of things here below, there is no need to ascribe causality to
the heavenly bodies.
Objection 3: Further, the agent produces its like. Now it is to be observed
that everything which is produced here below is produced through the
action of heat and cold, moisture and dryness, and other such qualities,
which do not exist in heavenly bodies. Therefore the heavenly bodies are
not the cause of what is produced here below.
Objection 4: Further, Augustine says (De Civ. Dei v, 6): "Nothing is more
corporeal than sex." But sex is not caused by the heavenly bodies: a sign
of this is that of twins born under the same constellation, one may be
male, the other female. Therefore the heavenly bodies are not the cause
of things produced in bodies here below.
On the contrary, Augustine says (De Trin. iii, 4): "Bodies of a grosser
and inferior nature are ruled in a certain order by those of a more
subtle and powerful nature." And Dionysius (Div. Nom. iv) says that "the
light of the sun conduces to the generation of sensible bodies, moves
them to life, gives them nourishment, growth, and perfection."
I answer that, Since every multitude proceeds from unity; and since what
is immovable is always in the same way of being, whereas what is moved
has many ways of being: it must be observed that throughout the whole of
nature, all movement proceeds from the immovable. Therefore the more
immovable certain things are, the more are they the cause of those things
which are most movable. Now the heavenly bodies are of all bodies the
most immovable, for they are not moved save locally. Therefore the
movements of bodies here below, which are various and multiform, must be
referred to the movement of the heavenly bodies, as to their cause.
Reply to Objection 1: These words of Damascene are to be understood as denying
that the heavenly bodies are the first cause of generation and corruption
here below; for this was affirmed by those who held that the heavenly
bodies are gods.
Reply to Objection 2: The active principles of bodies here below are only the
active qualities of the elements, such as hot and cold and the like. If
therefore the substantial forms of inferior bodies were not diversified
save according to accidents of that kind, the principles of which the
early natural philosophers held to be the "rare" and the "dense"; there
would be no need to suppose some principle above these inferior bodies,
for they would be of themselves sufficient to act. But to anyone who
considers the matter aright, it is clear that those accidents are merely
material dispositions in regard to the substantial forms of natural
bodies. Now matter is not of itself sufficient to act. And therefore it
is necessary to suppose some active principle above these material
This is why the Platonists maintained the existence of separate species,
by participation of which the inferior bodies receive their substantial
forms. But this does not seem enough. For the separate species, since
they are supposed to be immovable, would always have the same mode of
being: and consequently there would be no variety in the generation and
corruption of inferior bodies: which is clearly false.
Therefore it is necessary, as the Philosopher says (De Gener. ii, 10),
to suppose a movable principle, which by reason of its presence or
absence causes variety in the generation and corruption of inferior
bodies. Such are the heavenly bodies. Consequently whatever generates
here below, moves to the production of the species, as the instrument of
a heavenly body: thus the Philosopher says (Phys. ii, 2) that "man and
the sun generate man."
Reply to Objection 3: The heavenly bodies have not a specific likeness to the
bodies here below. Their likeness consists in this, that by reason of
their universal power, whatever is generated in inferior bodies, is
contained in them. In this way also we say that all things are like God.
Reply to Objection 4: The actions of heavenly bodies are variously received in
inferior bodies, according to the various dispositions of matter. Now it
happens at times that the matter in the human conception is not wholly
disposed to the male sex; wherefore it is formed sometimes into a male,
sometimes into a female. Augustine quotes this as an argument against
divination by stars: because the effects of the stars are varied even in
corporeal things, according to the various dispositions of matter.
Article 4: Whether the heavenly bodies are the cause of human actions?
Objection 1: It would seem that the heavenly bodies are the cause of human
actions. For since the heavenly bodies are moved by spiritual
substances, as stated above (Question , Article ), they act by virtue thereof as
their instruments. But those spiritual substances are superior to our
souls. Therefore it seems that they can cause impressions on our souls,
and thereby cause human actions.
Objection 2: Further, every multiform is reducible to a uniform principle. But
human actions are various and multiform. Therefore it seems that they are
reducible to the uniform movements of heavenly bodies, as to their
Objection 3: Further, astrologers often foretell the truth concerning the
outcome of wars, and other human actions, of which the intellect and will
are the principles. But they could not do this by means of the heavenly
bodies, unless these were the cause of human actions. Therefore the
heavenly bodies are the cause of human actions.
On the contrary, Damascene says (De Fide Orth. ii, 7) that "the heavenly
bodies are by no means the cause of human actions."
I answer that, The heavenly bodies can directly and of themselves act on
bodies, as stated above (Article ). They can act directly indeed on those
powers of the soul which are the acts of corporeal organs, but
accidentally: because the acts of such powers must needs be hindered by
obstacles in the organs; thus an eye when disturbed cannot see well.
Wherefore if the intellect and will were powers affixed to corporeal
organs, as some maintained, holding that intellect does not differ from
sense; it would follow of necessity that the heavenly bodies are the
cause of human choice and action. It would also follow that man is led by
natural instinct to his actions, just as other animals, in which there
are powers other than those which are affixed to corporeal organs: for
whatever is done here below in virtue of the action of heavenly bodies,
is done naturally. It would therefore follow that man has no free-will,
and that he would have determinate actions, like other natural things.
All of which is manifestly false, and contrary to human habit. It must be
observed, however, that indirectly and accidentally, the impressions of
heavenly bodies can reach the intellect and will, forasmuch, namely, as
both intellect and will receive something from the inferior powers which
are affixed to corporeal organs. But in this the intellect and will are
differently situated. For the intellect, of necessity, receives from the
inferior apprehensive powers: wherefore if the imaginative, cogitative,
or memorative powers be disturbed, the action of the intellect is, of
necessity, disturbed also. The will, on the contrary, does not, of
necessity, follow the inclination of the inferior appetite; for although
the passions in the irascible and concupiscible have a certain force in
inclining the will; nevertheless the will retains the power of following
the passions or repressing them. Therefore the impressions of the
heavenly bodies, by virtue of which the inferior powers can be changed,
has less influence on the will, which is the proximate cause of human
actions, than on the intellect.
To maintain therefore that heavenly bodies are the cause of human
actions is proper to those who hold that intellect does not differ from
sense. Wherefore some of these said that "such is the will of men, as is
the day which the father of men and of gods brings on" (Odyssey xviii
135). Since, therefore, it is manifest that intellect and will are not
acts of corporeal organs, it is impossible that heavenly bodies be the
cause of human actions.
Reply to Objection 1: The spiritual substances, that move the heavenly bodies, do
indeed act on corporeal things by means of the heavenly bodies; but they
act immediately on the human intellect by enlightening it. On the other
hand, they cannot compel the will, as stated above (Question , Article ).
Reply to Objection 2: Just as the multiformity of corporeal movements is
reducible to the uniformity of the heavenly movement as to its cause: so
the multiformity of actions proceeding from the intellect and the will is
reduced to a uniform principle which is the Divine intellect and will.
Reply to Objection 3: The majority of men follow their passions, which are
movements of the sensitive appetite, in which movements of the heavenly
bodies can cooperate: but few are wise enough to resist these passions.
Consequently astrologers are able to foretell the truth in the majority
of cases, especially in a general way. But not in particular cases; for
nothing prevents man resisting his passions by his free-will. Wherefore
the astrologers themselves are wont to say that "the wise man is stronger
than the stars" [*Ptolemy, Centiloquium, prop. 5], forasmuch as, to wit,
he conquers his passions.
Article 5: Whether heavenly bodies can act on the demons?
Objection 1: It would seem that heavenly bodies can act on the demons. For the
demons, according to certain phases of the moon, can harass men, who on
that account are called lunatics, as appears from Mt. 4:24 and 17:14. But
this would not be if they were not subject to the heavenly bodies.
Therefore the demons are subject to them.
Objection 2: Further, necromancers observe certain constellations in order to
invoke the demons. But these would not be invoked through the heavenly
bodies unless they were subject to them. Therefore they are subject to
Objection 3: Further, heavenly bodies are more powerful than inferior bodies.
But the demons are confined to certain inferior bodies, namely, "herbs,
stones, animals, and to certain sounds and words, forms and figures," as
Porphyry says, quoted by Augustine (De Civ. Dei x, 11). Much more
therefore are the demons subject to the action of heavenly bodies.
On the contrary, The demons are superior in the order of nature, to the
heavenly bodies. But the "agent is superior to the patient," as Augustine
says (Gen. ad lit. xii, 16). Therefore the demons are not subject to the
action of heavenly bodies.
I answer that, There have been three opinions about the demons. In the
first place the Peripatetics denied the existence of demons; and held
that what is ascribed to the demons, according to the necromantic art, is
effected by the power of the heavenly bodies. This is what Augustine (De
Civ. Dei x, 11) relates as having been held by Porphyry, namely, that "on
earth men fabricate certain powers useful in producing certain effects of
the stars." But this opinion is manifestly false. For we know by
experience that many things are done by demons, for which the power of
heavenly bodies would in no way suffice: for instance, that a man in a
state of delirium should speak an unknown tongue, recite poetry and
authors of whom he has no previous knowledge; that necromancers make
statues to speak and move, and other like things.
For this reason the Platonists were led to hold that demons are "animals
with an aerial body and a passive soul," as Apuleius says, quoted by
Augustine (De Civ. Dei viii, 16). And this is the second of the opinions
mentioned above: according to which it could be said that demons are
subject to heavenly bodies in the same way as we have said man is subject
thereto (Article ). But this opinion is proved to be false from what we have
said above (Question , Article ): for we hold that demons are spiritual
substances not united to bodies. Hence it is clear that they are subject
to the action of heavenly bodies neither essentially nor accidentally,
neither directly nor indirectly.
Reply to Objection 1: That demons harass men, according to certain phases of the
moon, happens in two ways. Firstly, they do so in order to "defame God's
creature," namely, the moon; as Jerome (In Matt. iv, 24) and Chrysostom
(Hom. lvii in Matt.) say. Secondly, because as they are unable to effect
anything save by means of the natural forces, as stated above (Question , Article , ad 2) they take into account the aptitude of bodies for the
intended result. Now it is manifest that "the brain is the most moist of
all the parts of the body," as Aristotle says [*De Part. Animal. ii, 7:
De Sens. et Sensato ii: De Somn. et Vigil. iii]: wherefore it is the most
subject to the action of the moon, the property of which is to move what
is moist. And it is precisely in the brain that animal forces culminate:
wherefore the demons, according to certain phases of the moon, disturb
man's imagination, when they observe that the brain is thereto disposed.
Reply to Objection 2: Demons when summoned through certain constellations, come
for two reasons. Firstly, in order to lead man into the error of
believing that there is some Divine power in the stars. Secondly, because
they consider that under certain constellations corporeal matter is
better disposed for the result for which they are summoned.
Reply to Objection 3: As Augustine says (De Civ. Dei xxi, 6), the "demons are
enticed through various kinds of stones, herbs, trees, animals, songs,
rites, not as an animal is enticed by food, but as a spirit by signs";
that is to say, forasmuch as these things are offered to them in token of
the honor due to God, of which they are covetous.
Article 6: Whether heavenly bodies impose necessity on things subject to their action?
Objection 1: It would seem that heavenly bodies impose necessity on things
subject to their action. For given a sufficient cause, the effect follows
of necessity. But heavenly bodies are a sufficient cause of their
effects. Since, therefore, heavenly bodies, with their movements and
dispositions, are necessary beings; it seems that their effects follow of
Objection 2: Further, an agent's effect results of necessity in matter, when
the power of the agent is such that it can subject the matter to itself
entirely. But the entire matter of inferior bodies is subject to the
power of heavenly bodies, since this is a higher power than theirs.
Therefore the effect of the heavenly bodies is of necessity received in
Objection 3: Further, if the effect of the heavenly body does not follow of
necessity, this is due to some hindering cause. But any corporeal cause,
that might possibly hinder the effect of a heavenly body, must of
necessity be reducible to some heavenly principle: since the heavenly
bodies are the causes of all that takes place here below. Therefore,
since also that heavenly principle is necessary, it follows that the
effect of the heavenly body is necessarily hindered. Consequently it
would follow that all that takes place here below happens of necessity.
On the contrary, The Philosopher says (De Somn. et Vigil. [*De Divin.
per Somn. ii]): "It is not incongruous that many of the signs observed in
bodies, of occurrences in the heavens, such as rain and wind, should not
be fulfilled." Therefore not all the effects of heavenly bodies take
place of necessity.
I answer that, This question is partly solved by what was said above
(Article ); and in part presents some difficulty. For it was shown that
although the action of heavenly bodies produces certain inclinations in
corporeal nature, the will nevertheless does not of necessity follow
these inclinations. Therefore there is nothing to prevent the effect of
heavenly bodies being hindered by the action of the will, not only in man
himself, but also in other things to which human action extends.
But in natural things there is no such principle, endowed with freedom
to follow or not to follow the impressions produced by heavenly agents.
Wherefore it seems that in such things at least, everything happens of
necessity; according to the reasoning of some of the ancients who
supposing that everything that is, has a cause; and that, given the
cause, the effect follows of necessity; concluded that all things happen
of necessity. This opinion is refuted by Aristotle (Metaph. vi, Did. v,
3) as to this double supposition.
For in the first place it is not true that, given any cause whatever,
the effect must follow of necessity. For some causes are so ordered to
their effects, as to produce them, not of necessity, but in the majority
of cases, and in the minority to fail in producing them. But that such
cases do fail in the minority of cases is due to some hindering cause;
consequently the above-mentioned difficulty seems not to be avoided,
since the cause in question is hindered of necessity.
Therefore we must say, in the second place, that everything that is a
being "per se," has a cause; but what is accidentally, has not a cause,
because it is not truly a being, since it is not truly one. For (that a
thing is) "white" has a cause, likewise (that a man is) "musical" has not
a cause, but (that a being is) "white-musical" has not a cause, because
it is not truly a being, nor truly one. Now it is manifest that a cause
which hinders the action of a cause so ordered to its effect as to
produce it in the majority of cases, clashes sometimes with this cause by
accident: and the clashing of these two causes, inasmuch as it is
accidental, has no cause. Consequently what results from this clashing of
causes is not to be reduced to a further pre-existing cause, from which
it follows of necessity. For instance, that some terrestrial body take
fire in the higher regions of the air and fall to the earth, is caused by
some heavenly power: again, that there be on the surface of the earth
some combustible matter, is reducible to some heavenly principle. But
that the burning body should alight on this matter and set fire to it, is
not caused by a heavenly body, but is accidental. Consequently not all
the effects of heavenly bodies result of necessity.
Reply to Objection 1: The heavenly bodies are causes of effects that take place
here below, through the means of particular inferior causes, which can
fail in their effects in the minority of cases.
Reply to Objection 2: The power of a heavenly body is not infinite. Wherefore it
requires a determinate disposition in matter, both as to local distance
and as to other conditions, in order to produce its effect. Therefore as
local distance hinders the effect of a heavenly body (for the sun has not
the same effect in heat in Dacia as in Ethiopia); so the grossness of
matter, its low or high temperature or other such disposition, can hinder
the effect of a heavenly body.
Reply to Objection 3: Although the cause that hinders the effect of another cause
can be reduced to a heavenly body as its cause; nevertheless the clashing
of two causes, being accidental, is not reduced to the causality of a
heavenly body, as stated above.