Dist. 13, Art. 3, Q. 2
by St. Bonaventure
Source text: Public Domain Mark 1.0. English translation/apparatus/encoding: CC BY-NC 4.0, Wroot Press.
https://bonaventure.wrootpress.com/browse/2/d/13/q/bon-sent-II-d13-a3-q2
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### Question II. *Whether lumen is a substantial form or an accidental one.*

Secondly it is asked whether *lumen* is a substantial form or an accidental one. And that it is an accidental form is shown.

*Fundamenta.*

1. That which comes upon something already complete *in being* is accidental; but lumen comes upon air already complete in being: therefore it is accidental.

2. Likewise, «*that which is present and absent apart from the corruption of the subject is an accident*»; lumen is present and absent apart from the corruption of the air, which is its subject: therefore etc.

3. Likewise, as color stands to a terminated body, so lumen stands to a transparent body; but color is an accident in the terminated body: therefore lumen is an accident in the transparent body.

4. Likewise, if one of opposites, existing in a subject, is an accident, the other is also an accident; but obscuration happens to air itself: therefore by parity of reasoning so does illumination.

*To the contrary:*

1. It is impossible that two accidents of the same species be in the same subject, because an accident is numbered by the subject in which it is: but two *lumina*, as Dionysius says, are in the same air medium: therefore it is impossible that lumen be an accident of the air.

2. Likewise, an accident, when it is generated, has its origin from the proper principles of the subject, and when it is resolved, is resolved into its subject; but lumen is neither educed out of air nor resolved into air: therefore lumen is not an accident of air. And it is settled that it is in air: therefore if it is not an accident of it, it is an accident of nothing.

3. Likewise, no accident passes from subject to subject; but a ray is transferred from one part of air to another, and lumen likewise: therefore lumen cannot be an accident.

4. Likewise, no accident remains immobile when that in which it is is moved; but a ray remains immobile when the air is moved: therefore the ray is not an accident. If you say this is because lumen in the medium has *spiritual being*, like an idolum; against this it is objected that ray and lumen there have natural operation and the principle of a natural operation: therefore it seems that it is there *naturally* and concretely, not *spiritually* and abstractly.

### CONCLUSION.

> *Lumen in the medium, insofar as it denotes an active power, denotes a substance having the mode of an accident; insofar as it denotes a sensible quality, it denotes an accident — one which does not fully have the character of a natural accident, but [the character] of a likeness or intention.*

**I respond:** For the understanding of the foregoing it is to be noted that on this point there is a threefold way of speaking, each of which presupposes that lumen in the medium is some form or quality.

*Opinion 1.* For some say that lumen in the medium is a *substance*; yet it exists in the medium *by the mode of an accident*, because it is not substantial to the air itself; and they say this because the generation of lumen from lux is by the way of univocation; and so, since lux is a substantial form in its source, they say that lumen is a substance *in the medium*, although it has an accidental mode of being — especially since there does not seem to be any other essence belonging to lumen and lux, but only that they seem to differ by mode of being or by *esse*.

But because lumen in the medium is that which *Opinion 2.* is most especially sensed and which makes other things to be sensed; therefore there is a second position, that lumen in the medium is an *accident*; for it is not caused by the luminous body except insofar as it is shining; and so it is an accident by comparison to the *principle from which*. They also say that it is an accident by comparison to the *subject in which*, because it comes upon [something] already complete and can be present and absent apart from the corruption of the subject; and thus lumen in the medium has the full character of an accident, though not by comparison to the same [term]. For an accident is wont to be compared to a substance as to *subject* and *cause*; but lumen, although it has to be compared to substance in these two modes, [is compared] not to the same one, because it is compared to air as to subject, since it is in it; to the luminous body, as to principle, since it is from it.

But because lumen, insofar as it exists in the medium, is sensed of itself, so that, placed before the sense, it makes [it] sense; and again, in the same part of the medium it can be multiplied without confusion, according to the position of Dionysius: therefore there is a *Opinion 3.* third position, that lumen in the medium is neither substance nor accident properly, because it does not have there *natural being* concrete with matter, but *spiritual* and abstract [being]. Hence they say that, just as the species of color in the medium is compared to the color existing in the object body, so lumen in the medium [is compared] to the lux existing in the luminous body. — *Improbatur.* But since lumen in the medium has not only a *spiritual* operation upon the soul but also a *natural* one upon natural bodies, it seems to be in the air not only in a spiritual mode (i.e. to be there by the mode of a habit) but also in some way according to natural being; and so it seems that this is not enough to say, although it seems very probable.

*Judgement on the foregoing.* Therefore it is to be understood that all the above ways contain something of truth in themselves, and from all these one integral truth is elicited; which is clear thus. — *Lumen denotes 1. an active power.* For lumen in the medium denotes an *active power*, going forth from the luminous body, by which the luminous body acts and impresses upon these lower things; and this is a power substantial to the body itself. And of this Damascene says that lumen, which is from fire, is not something ministerial to fire itself or accidental, but a power connatural and consubstantial to it, as is clear in the authority adduced in the preceding problem; and this power is not perceptible by sense, nor does it operate only in the sense of sight, but it also conduces to the eduction of all the senses into act, as Augustine says in the seventh [book] *On Genesis according to the Letter*, which was held in a certain authority previously adduced. Thus also the philosophers say that the celestial body, by means of its lumen, influences down to the depths of the earth, where mineral bodies are wont to be generated. And as to this, those say truly who say that *lumen denotes substance accidentally compared to air*, just as the power of an agent is in a certain way accidentally compared to that which carries [it].

*2. a sensible quality.* But lumen denotes not only that active power, which sense does not perceive, but also a certain *sensible quality*, by which the sense of sight is made actually sensing; and that is an accidental quality in the third species of quality. And accordingly Avicenna says in the book *On the Natural Sufficiency* that «*lumen is an affection of a body having lux, when its opposite is present to it*», namely the pervious. And so that second opinion was speaking truly, which said that lumen is an *accident*, not only by comparison to the air in which it is received, but also in comparison to the body by which it is caused, since it arises from it inasmuch as that is shining and has being as an object of sense.

*Notandum.* According to each of these natures found in lumen, lumen is compared to the air not as to a *first subject*, but as to a *carrier* and to a *medium*; and therefore by comparison to the air itself it does not have a *natural* mode of existing, but [exists] by the mode of a *habit*; nor is it a natural form, but rather a likeness of one; just as a species in the medium is not *properly color*, but *as color* or a likeness of color. Yet it has the maximum approximation to it; and it rests upon it so closely that it does not need an extrinsic principle out of which it may be educed. Hence lumen in the medium does not have a material principle

out of which, but rather an originative one, from which it flows and to which it also returns when it ceases to be in the medium, as is said of a likeness. And in this way the Commentator on the second [book] *On the Soul* says that *lux* is the habit of the diaphanous, and that it is in it as intention or species or likeness. And as to this fourth point the third opinion was speaking truly.

*Conclusion as to the members.* From these things, therefore, it is clear that lumen in the medium, insofar as it denotes *active power*, denotes *substance* having the mode of *accident*; insofar as it denotes *sensible quality*, it denotes *accident*. But that accident, referred to air, does not fully have the character of a *natural accident*, but [that] of a likeness or intention, because it is there not as in a sustaining subject, but as in a carrier. — From these things the answers to both sides are clear.

*To the fundamenta.*

*1. 2.* As for the objection that it comes upon [something] already complete and recedes apart from the corruption of the subject, this shows that it has the *mode of an accident*, according as it is in the medium.

*3. 4.* As for the objection that it stands in the mode of color and is a sensible quality, this speaks of lumen according as it has in itself the *nature of an accident*.

*To the contrary [arguments].* The reasons on the contrary, which prove that it is not an *accident* — because it is not numbered by the numbering of the subject, because it is not moved at the motion of the air, because it is not caused by the air nor resolved into the air — conclude only that it does not there have *fully the character of a natural accident*; *On the natural accident.* which is compared to that in which it is as to subject and cause, and which is also sustained and depends upon that in which it is principally and is joined to it by an inseparable bond. — *On lumen as accident.* But this is not the case in the matter at hand, because lumen, although it is in air, is caused by the luminous body and depends upon it principally; nor is it in air as in a sustainer, but as in a carrier; and therefore it receives duration and change and numbering rather from the *lucid [body] which influences* than from the *air which receives*. And on this account Dionysius says that many *lumina* are in the same medium unconfused, and are torn apart or separated from one another according to the withdrawal of the illuminating bodies. For that distinction is owing to the continuation of the *lumina* with their origin, from which they proceed naturally and by whose power they act, although in the medium they are in a certain way *spiritually* and abstractly. And thus the other things asked about this matter are now clear.