If the severance of the air by such bodies leaves it unaffected, why must there be any severance before the images of sight can reach us?
And, further, once we reject the theory that these images reach us by way of some outstreaming from the objects seen, there is no reason to think of the air being affected and passing on to us, in a progression of impression, what has been impressed upon itself.
If our perception is to depend upon previous impressions made upon the air, then we have no direct knowledge of the object of vision, but know it only as through an intermediary, in the same way as we are aware of warmth where it is not the distant fire itself that warms us, but the warmed intervening air.That is a matter of contact; but sight is not produced by contact: the application of an object to the eye would not produce sight; what is required is the illumination of the intervening medium; for the air in itself is a dark substance: If it were not for this dark substance there would probably be no reason for the existence of light: the dark intervening matter is a barrier, and vision requires that it be overcome by light.Perhaps also the reason why an object brought close to the eye cannot be seen is that it confronts us with a double obscuration, its own and that of the air.
3.For the most convincing proof that vision does not depend upon the transmission of impressions of any kind made upon the air, we have only to consider that in the darkness of night we can see a fire and the stars and their very shapes.
No one will pretend that these forms are reproduced upon the darkness and come to us in linked progression; if the fire thus rayed out its own form, there would be an end to the darkness.In the blackest night, when the very stars are hidden and show no gleam of their light, we can see the fire of the beacon-stations and of maritime signal-towers.
Now if, in defiance of all that the senses tell us, we are to believe that in these examples the fire [as light] traverses the air, then, in so far as anything is visible, it must be that dimmed reproduction in the air, not the fire itself.But if an object can be seen on the other side of some intervening darkness, much more would it be visible with nothing intervening.
We may hold one thing certain: the impossibility of vision without an intervening substance does not depend upon that absence in itself: the sole reason is that, with the absence, there would be an end to the sympathy reigning in the living whole and relating the parts to each other in an existent unity.
Perception of every kind seems to depend on the fact that our universe is a whole sympathetic to itself: that it is so, appears from the universal participation in power from member to member, and especially in remote power.
No doubt it would be worth enquiry- though we pass it for the present- what would take place if there were another kosmos, another living whole having no contact with this one, and the far ridges of our heavens had sight: would our sphere see that other as from a mutually present distance, or could there be no dealing at all from this to that?
To return; there is a further consideration showing that sight is not brought about by this alleged modification of the intervenient.
Any modification of the air substance would necessarily be corporeal: there must be such an impression as is made upon sealing wax.But this would require that each part of the object of vision be impressed on some corresponding portion of the intervenient: the intervenient, however, in actual contact with the eye would be just that portion whose dimensions the pupil is capable of receiving.But as a matter of fact the entire object appears before the pupil; and it is seen entire by all within that air space for a great extent, in front, sideways, close at hand, from the back, as long as the line of vision is not blocked.This shows that any given portion of the air contains the object of vision, in face view so to speak, and, at once, we are confronted by no merely corporeal phenomena; the facts are explicable only as depending upon the greater laws, the spiritual, of a living being one and self-sensitive.
4.But there is the question of the linked light that must relate the visual organ to its object.
Now, firstly: since the intervening air is not necessary- unless in the purely accidental sense that air may be necessary to light- the light that acts as intermediate in vision will be unmodified: vision depends upon no modification whatever.This one intermediate, light, would seem to be necessary, but, unless light is corporeal, no intervening body is requisite: and we must remember that intervenient and borrowed light is essential not to seeing in general but to distant vision; the question whether light absolutely requires the presence of air we will discuss later.For the present one matter must occupy us:
If, in the act of vision, that linked light becomes ensouled, if the soul or mind permeates it and enters into union with it, as it does in its more inward acts such as understanding- which is what vision really is- then the intervening light is not a necessity: the process of seeing will be like that of touch; the visual faculty of the soul will perceive by the fact of having entered into the light;all that intervenes remains unaffected, serving simply as the field over which the vision ranges.
This brings up the question whether the sight is made active over its field by the sheer presence of a distance spread before it, or by the presence of a body of some kind within that distance.
