QUESTION 67: ON THE WORK OF DISTINCTION IN ITSELF
We must consider next the work of distinction in itself. First, the work
of the first day; secondly, the work of the second day; thirdly the work
of the third day.
Under the first head there are four points of inquiry:
(1) Whether the word light is used in its proper sense in speaking of
(2) Whether light, in corporeal things, is itself corporeal?
(3) Whether light is a quality?
(4) Whether light was fittingly made on the first day?
Article 1: Whether the word "light" is used in its proper sense in speaking of spiritual things?
Objection 1: It would seem that "light" is used in its proper sense in
spiritual things. For Augustine says (Gen. ad lit. iv, 28) that "in
spiritual things light is better and surer: and that Christ is not called
Light in the same sense as He is called the Stone; the former is to be
taken literally, and the latter metaphorically."
Objection 2: Further, Dionysius (Div. Nom. iv) includes Light among the
intellectual names of God. But such names are used in their proper sense
in spiritual things. Therefore light is used in its proper sense in
Objection 3: Further, the Apostle says (Eph. 5:13): "All that is made manifest
is light." But to be made manifest belongs more properly to spiritual
things than to corporeal. Therefore also does light.
On the contrary, Ambrose says (De Fide ii) that "Splendor" is among
those things which are said of God metaphorically.
I answer that, Any word may be used in two ways---that is to say, either
in its original application or in its more extended meaning. This is
clearly shown in the word "sight," originally applied to the act of the
sense, and then, as sight is the noblest and most trustworthy of the
senses, extended in common speech to all knowledge obtained through the
other senses. Thus we say, "Seeing how it tastes," or "smells," or
"burns. "Further, sight is applied to knowledge obtained through the
intellect, as in those words: "Blessed are the clean of heart, for they
shall see God" (Mt. 5:8). And thus it is with the word light. In its
primary meaning it signifies that which makes manifest to the sense of
sight; afterwards it was extended to that which makes manifest to
cognition of any kind. If, then, the word is taken in its strict and
primary meaning, it is to be understood metaphorically when applied to
spiritual things, as Ambrose says (De Fide ii). But if taken in its
common and extended use, as applied to manifestation of every kind, it
may properly be applied to spiritual things.
The answer to the objections will sufficiently appear from what has been
Article 2: Whether light is a body?
Objection 1: It would seem that light is a body. For Augustine says (De Lib.
Arb. iii, 5) that "light takes the first place among bodies."Therefore
light is a body.
Objection 2: Further, the Philosopher says (Topic. v, 2) that "light is a
species of fire." But fire is a body, and therefore so is light.
Objection 3: Further, the powers of movement, intersection, reflection, belong
properly to bodies; and all these are attributes of light and its rays.
Moreover, different rays of light, as Dionysius says (Div. Nom. ii) are
united and separated, which seems impossible unless they are bodies.
Therefore light is a body.
On the contrary, Two bodies cannot occupy the same place simultaneously.
But this is the case with light and air. Therefore light is not a body.
I answer that, Light cannot be a body, for three evident reasons. First,
on the part of place. For the place of any one body is different from
that of any other, nor is it possible, naturally speaking, for any two
bodies of whatever nature, to exist simultaneously in the same place;
since contiguity requires distinction of place.
The second reason is from movement. For if light were a body, its
diffusion would be the local movement of a body. Now no local movement of
a body can be instantaneous, as everything that moves from one place to
another must pass through the intervening space before reaching the end:
whereas the diffusion of light is instantaneous. Nor can it be argued
that the time required is too short to be perceived; for though this may
be the case in short distances, it cannot be so in distances so great as
that which separates the East from the West. Yet as soon as the sun is at
the horizon, the whole hemisphere is illuminated from end to end. It must
also be borne in mind on the part of movement that whereas all bodies
have their natural determinate movement, that of light is indifferent as
regards direction, working equally in a circle as in a straight line.
Hence it appears that the diffusion of light is not the local movement of
The third reason is from generation and corruption. For if light were a
body, it would follow that whenever the air is darkened by the absence of
the luminary, the body of light would be corrupted, and its matter would
receive a new form. But unless we are to say that darkness is a body,
this does not appear to be the case. Neither does it appear from what
matter a body can be daily generated large enough to fill the intervening
hemisphere. Also it would be absurd to say that a body of so great a bulk
is corrupted by the mere absence of the luminary. And should anyone reply
that it is not corrupted, but approaches and moves around with the sun,
we may ask why it is that when a lighted candle is obscured by the
intervening object the whole room is darkened? It is not that the light
is condensed round the candle when this is done, since it burns no more
brightly then than it burned before.
Since, therefore, these things are repugnant, not only to reason, but to
common sense, we must conclude that light cannot be a body.
Reply to Objection 1: Augustine takes light to be a luminous body in act---in
other words, to be fire, the noblest of the four elements.
Reply to Objection 2: Aristotle pronounces light to be fire existing in its own
proper matter: just as fire in aerial matter is "flame," or in earthly
matter is "burning coal." Nor must too much attention be paid to the
instances adduced by Aristotle in his works on logic, as he merely
mentions them as the more or less probable opinions of various writers.
Reply to Objection 3: All these properties are assigned to light metaphorically,
and might in the same way be attributed to heat. For because movement
from place to place is naturally first in the order of movement as is
proved Phys. viii, text. 55, we use terms belonging to local movement in
speaking of alteration and movement of all kinds. For even the word
distance is derived from the idea of remoteness of place, to that of all
contraries, as is said Metaph. x, text. 13.
Article 3: Whether light is a quality?
Objection 1: It would seem that light is not a quality. For every quality
remains in its subject, though the active cause of the quality be
removed, as heat remains in water removed from the fire. But light does
not remain in the air when the source of light is withdrawn. Therefore
light is not a quality.
Objection 2: Further, every sensible quality has its opposite, as cold is
opposed to heat, blackness to whiteness. But this is not the case with
light since darkness is merely a privation of light. Light therefore is
not a sensible quality.
Objection 3: Further, a cause is more potent than its effect. But the light of
the heavenly bodies is a cause of substantial forms of earthly bodies,
and also gives to colors their immaterial being, by making them actually
visible. Light, then, is not a sensible quality, but rather a substantial
or spiritual form.
On the contrary, Damascene (De Fide Orth. i) says that light is a
species of quality.
I answer that, Some writers have said that the light in the air has not
a natural being such as the color on a wall has, but only an intentional
being, as a similitude of color in the air. But this cannot be the case
for two reasons. First, because light gives a name to the air, since by
it the air becomes actually luminous. But color does not do this, for we
do not speak of the air as colored. Secondly, because light produces
natural effects, for by the rays of the sun bodies are warmed, and
natural changes cannot be brought about by mere intentions. Others have
said that light is the sun's substantial form, but this also seems
impossible for two reasons. First, because substantial forms are not of
themselves objects of the senses; for the object of the intellect is what
a thing is, as is said De Anima iii, text. 26: whereas light is visible
of itself. In the second place, because it is impossible that what is the
substantial form of one thing should be the accidental form of another;
since substantial forms of their very nature constitute species:
wherefore the substantial form always and everywhere accompanies the
species. But light is not the substantial form of air, for if it were,
the air would be destroyed when light is withdrawn. Hence it cannot be
the substantial form of the sun.
We must say, then, that as heat is an active quality consequent on the
substantial form of fire, so light is an active quality consequent on the
substantial form of the sun, or of another body that is of itself
luminous, if there is any such body. A proof of this is that the rays of
different stars produce different effects according to the diverse
natures of bodies.
Reply to Objection 1: Since quality is consequent upon substantial form, the mode
in which the subject receives a quality differs as the mode differs in
which a subject receives a substantial form. For when matter receives its
form perfectly, the qualities consequent upon the form are firm and
enduring; as when, for instance, water is converted into fire. When,
however, substantial form is received imperfectly, so as to be, as it
were, in process of being received, rather than fully impressed, the
consequent quality lasts for a time but is not permanent; as may be seen
when water which has been heated returns in time to its natural state.
But light is not produced by the transmutation of matter, as though
matter were in receipt of a substantial form, and light were a certain
inception of substantial form. For this reason light disappears on the
disappearance of its active cause.
Reply to Objection 2: It is accidental to light not to have a contrary, forasmuch as it is the natural quality of the first corporeal cause of change, which is itself removed from contrariety.
Reply to Objection 3: As heat acts towards perfecting the form of fire, as an
instrumental cause, by virtue of the substantial form, so does light act
instrumentally, by virtue of the heavenly bodies, towards producing
substantial forms; and towards rendering colors actually visible,
inasmuch as it is a quality of the first sensible body.
Article 4: Whether the production of light is fittingly assigned to the first day?
Objection 1: It would seem that the production of light is not fittingly
assigned to the first day. For light, as stated above (Article ), is a
quality. But qualities are accidents, and as such should have, not the
first, but a subordinate place. The production of light, then, ought not
to be assigned to the first day.
Objection 2: Further, it is light that distinguishes night from day, and this
is effected by the sun, which is recorded as having been made on the
fourth day. Therefore the production of light could not have been on the
Objection 3: Further, night and day are brought about by the circular movement
of a luminous body. But movement of this kind is an attribute of the
firmament, and we read that the firmament was made on the second day.
Therefore the production of light, dividing night from day, ought not to
be assigned to the first day.
Objection 4: Further, if it be said that spiritual light is here spoken of, it
may be replied that the light made on the first day dispels the darkness.
But in the beginning spiritual darkness was not, for even the demons were
in the beginning good, as has been shown (Question , Article ). Therefore the
production of light ought not to be assigned to the first day.
On the contrary, That without which there could not be day, must have
been made on the first day. But there can be no day without light.
Therefore light must have been made on the first day.
I answer that, There are two opinions as to the production of light.
Augustine seems to say (De Civ. Dei xi, 9,33) that Moses could not have
fittingly passed over the production of the spiritual creature, and
therefore when we read, "In the beginning God created heaven and earth,"
a spiritual nature as yet formless is to be understood by the word
"heaven," and formless matter of the corporeal creature by the word
"earth." And spiritual nature was formed first, as being of higher
dignity than corporeal. The forming, therefore, of this spiritual nature
is signified by the production of light, that is to say, of spiritual
light. For a spiritual nature receives its form by the enlightenment
whereby it is led to adhere to the Word of God.
Other writers think that the production of spiritual creatures was
purposely omitted by Moses, and give various reasons. Basil [*Hom. i in
Hexaem.] says that Moses begins his narrative from the beginning of time
which belongs to sensible things; but that the spiritual or angelic
creation is passed over, as created beforehand.
Chrysostom [*Hom. ii in Genes.] gives as a reason for the omission that
Moses was addressing an ignorant people, to whom material things alone
appealed, and whom he was endeavoring to withdraw from the service of
idols. It would have been to them a pretext for idolatry if he had spoken
to them of natures spiritual in substance and nobler than all corporeal
creatures; for they would have paid them Divine worship, since they were
prone to worship as gods even the sun, moon, and stars, which was
forbidden them (Dt. 4).
But mention is made of several kinds of formlessness, in regard to the
corporeal creature. One is where we read that "the earth was void and
empty," and another where it is said that "darkness was upon the face of
the deep." Now it seems to be required, for two reasons, that the
formlessness of darkness should be removed first of all by the production
of light. In the first place because light is a quality of the first
body, as was stated (Article ), and thus by means of light it was fitting
that the world should first receive its form. The second reason is
because light is a common quality. For light is common to terrestrial and
celestial bodies. But as in knowledge we proceed from general principles,
so do we in work of every kind. For the living thing is generated before
the animal, and the animal before the man, as is shown in De Gener. Anim.
ii, 3. It was fitting, then, as an evidence of the Divine wisdom, that
among the works of distinction the production of light should take first
place, since light is a form of the primary body, and because it is more
Basil [*Hom. ii in Hexaem.], indeed, adds a third reason: that all other
things are made manifest by light. And there is yet a fourth, already
touched upon in the objections; that day cannot be unless light exists,
which was made therefore on the first day.
Reply to Objection 1: According to the opinion of those who hold that the
formlessness of matter preceded its form in duration, matter must be held
to have been created at the beginning with substantial forms, afterwards
receiving those that are accidental, among which light holds the first
Reply to Objection 2: In the opinion of some the light here spoken of was a kind
of luminous nebula, and that on the making of the sun this returned to
the matter of which it had been formed. But this cannot well be
maintained, as in the beginning of Genesis Holy Scripture records the
institution of that order of nature which henceforth is to endure. We
cannot, then, say that what was made at that time afterwards ceased to
Others, therefore, held that this luminous nebula continues in
existence, but so closely attached to the sun as to be indistinguishable.
But this is as much as to say that it is superfluous, whereas none of
God's works have been made in vain. On this account it is held by some
that the sun's body was made out of this nebula. This, too, is impossible
to those at least who believe that the sun is different in its nature
from the four elements, and naturally incorruptible. For in that case its
matter cannot take on another form.
I answer, then, with Dionysius (Div. Nom. iv), that the light was the
sun's light, formless as yet, being already the solar substance, and
possessing illuminative power in a general way, to which was afterwards
added the special and determinative power required to produce determinate
effects. Thus, then, in the production of this light a triple distinction
was made between light and darkness. First, as to the cause, forasmuch as
in the substance of the sun we have the cause of light, and in the opaque
nature of the earth the cause of darkness. Secondly, as to place, for in
one hemisphere there was light, in the other darkness. Thirdly, as to
time; because there was light for one and darkness for another in the
same hemisphere; and this is signified by the words, "He called the light
day, and the darkness night."
Reply to Objection 3: Basil says (Hom. ii in Hexaem.) that day and night were
then caused by expansion and contraction of light, rather than by
movement. But Augustine objects to this (Gen. ad lit. i), that there was
no reason for this vicissitude of expansion and contraction since there
were neither men nor animals on the earth at that time, for whose service
this was required. Nor does the nature of a luminous body seem to admit
of the withdrawal of light, so long as the body is actually present;
though this might be effected by a miracle. As to this, however,
Augustine remarks (Gen. ad lit. i) that in the first founding of the
order of nature we must not look for miracles, but for what is in
accordance with nature. We hold, then, that the movement of the heavens
is twofold. Of these movements, one is common to the entire heaven, and
is the cause of day and night. This, as it seems, had its beginning on
the first day. The other varies in proportion as it affects various
bodies, and by its variations is the cause of the succession of days,
months, and years. Thus it is, that in the account of the first day the
distinction between day and night alone is mentioned; this distinction
being brought about by the common movement of the heavens. The further
distinction into successive days, seasons, and years recorded as begun on
the fourth day, in the words, "let them be for seasons, and for days, and
years" is due to proper movements.
Reply to Objection 4: As Augustine teaches (Confess. xii; Gen. ad lit. 1,15),
formlessness did not precede forms in duration; and so we must understand
the production of light to signify the formation of spiritual creatures,
not, indeed, with the perfection of glory, in which they were not
created, but with the perfection of grace, which they possessed from
their creation as said above (Question , Article ). Thus the division of light
from darkness will denote the distinction of the spiritual creature from
other created things as yet without form. But if all created things
received their form at the same time, the darkness must be held to mean
the spiritual darkness of the wicked, not as existing from the beginning
but such as God foresaw would exist.