1. We undertook to discuss the question whether sight is possible in the absence of any intervening medium, such as air or some other form of what is known as transparent body: this is the time and place.

It has been explained that seeing and all sense-perception can occur only through the medium of some bodily substance, since in the absence of body the soul is utterly absorbed in the Intellectual Sphere. Sense-perception being the gripping not of the Intellectual but of the sensible alone, the soul, if it is to form any relationship of knowledge, or of impression, with objects of sense, must be brought in some kind of contact with them by means of whatever may bridge the gap.

The knowledge, then, is realized by means of bodily organs: through these, which [in the embodied soul] are almost of one growth with it, being at least its continuations, it comes into something like unity with the alien, since this mutual approach brings about a certain degree of identity [which is the basis of knowledge].

Admitting, then, that some contact with an object is necessary for knowing it, the question of a medium falls to the ground in the case of things identified by any form of touch; but in the case of sight -- we leave hearing over for the present -- we are still in doubt; is there need of some bodily substance between the eye and the illumined object?

No: such an intervening material may be a favouring circumstance, but essentially it adds nothing to seeing power.

Dense bodies, such as clay, actually prevent sight; the less material the intervening substance is, the more clearly we see; the intervening substance, then, is a hindrance, or, if not that, at least not a help.

It will be objected that vision implies that whatever intervenes between seen and seer must first [and progressively] experience the object and be, as it were, shaped to it; we will be reminded that [vision is not a direct and single relation between agent and object, but is the perception of something radiated since] anyone facing to the object from the side opposite to ourselves sees it equally; we will be asked to deduce that if all the space intervening between seen and seer did not carry the impression of the object we could not receive it.

But all the need is met when the impression reaches that which is adapted to receive it; there is no need for the intervening space to be impressed. If it is, the impression will be of quite another order: the rod between the fisher's hand and the torpedo fish is not affected in the same way as the hand that feels the shock. And yet there too, if rod and line did not intervene, the hand would not be affected -- though even that may be questioned, since after all the fisherman, we are told, is numbed if the torpedo merely lies in his net.

The whole matter seems to bring us back to that sympathy of which we have treated. If a certain thing is of a nature to be sympathetically affected by another in virtue of some similitude between them, then anything intervening, not sharing in that similitude, will not be affected, or at least not similarly. If this be so, anything naturally disposed to be affected will take the impression more vividly in the absence of intervening substance, even of some substance capable, itself, of being affected.

2. If sight depends upon the linking of the light of vision with the light leading progressively to the illumined object, then, by the very hypothesis, one intervening substance, the light, is indispensable: but if the illuminated body, which is the object of vision, serves as an agent operating certain changes, some such change might very well impinge immediately upon the eye, requiring no medium; this all the more, since as things are the intervening substance, which actually does exist, is in some degree changed at the point of contact with the eye [and so cannot be in itself a requisite to vision].

Those who have made vision a forth-going act [and not an in-coming from the object] need not postulate an intervening substance -- unless, indeed, to provide against the ray from the eye failing on its path -- but this is a ray of light and light flies straight. Those who make vision depend upon resistance are obliged to postulate an intervening substance.

The champions of the image, with its transit through a void, are seeking the way of least resistance; but since the entire absence of intervenient gives a still easier path they will not oppose that hypothesis.

So, too, those that explain vision by sympathy must recognize that an intervening substance will be a hindrance as tending to check or block or enfeeble that sympathy; this theory, especially, requires the admission that any intervenient, and particularly one of kindred nature, must blunt the perception by itself absorbing part of the activity. Apply fire to a body continuous through and through, and no doubt the core will be less affected than the surface: but where we are dealing with the sympathetic parts of one living being, there will scarcely be less sensation because of the intervening substance, or, if there should be, the degree of sensation will still be proportionate to the nature of the separate part, with the intervenient acting merely as a certain limitation; this, though, will not be the case where the element introduced is of a kind to overleap the bridge.

But this is saying that the sympathetic quality of the universe depends upon its being one living thing, and that our amenability to experience depends upon our belonging integrally to that unity; would it not follow that continuity is a condition of any perception of a remote object?

The explanation is that continuity and its concomitant, the bridging substance, come into play because a living being must be a continuous thing, but that, none the less, the receiving of impression is not an essentially necessary result of continuity; if it were, everything would receive such impression from everything else, and if thing is affected by thing in various separate orders, there can be no further question of any universal need of intervening substance.

Why it should be especially requisite in the act of seeing would have to be explained: in general, an object passing through the air does not affect it beyond dividing it; when a stone falls, the air simply yields; nor is it reasonable to explain the natural direction of movement by resistance; to do so would bring us to the absurdity that resistance accounts for the upward movement of fire, which on the contrary, overcomes the resistance of the air by its own essentially quick energy. If we are told that the resistance is brought more swiftly into play by the very swiftness of the ascending body, that would be a mere accidental circumstance, not a cause of the upward motion: in trees the upthrust from the root depends on no such external propulsion; we, too, in our movements cleave the air and are in no wise forwarded by its resistance; it simply flows in from behind to fill the void we make.

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.

If by the presence of such a body, then there will be vision though there be no intervenient; if the intervenient is the sole attractive agent, then we are forced to think of the visible object as being a Kind utterly without energy, performing no act. But so inactive a body cannot be: touch tells us that, for it does not merely announce that something is by and is touched: it is acted upon by the object so that it reports distinguishing qualities in it, qualities so effective that even at a distance touch itself would register them but for the accidental that it demands proximity.

We catch the heat of a fire just as soon as the intervening air does; no need to wait for it to be warmed: the denser body, in fact, takes in more warmth than the air has to give; in other words, the air transmits the heat but is not the source of our warmth.

When on the one side, that of the object, there is the power in any degree of an outgoing act, and on the other, that of the sight, the capability of being acted upon, surely the object needs no medium through which to be effective upon what it is fully equipped to affect: this would be needing not a help but a hindrance.

Or, again, consider the Dawn: there is no need that the light first flood the air and then come to us; the event is simultaneous to both: often, in fact, we see [in the distance] when the light is not as yet round our eyes at all but very far off, before, that is, the air has been acted upon: here we have vision without any modified intervenient, vision before the organ has received the light with which it is to be linked.

It is difficult to reconcile with this theory the fact of seeing stars or any fire by night.

If [as by the theory of an intervenient] the percipient mind or soul remains within itself and needs the light only as one might need a stick in the hand to touch something at a distance, then the perception will be a sort of tussle: the light must be conceived as something thrusting, something aimed at a mark, and similarly, the object, considered as an illuminated thing, must be conceived to be resistant; for this is the normal process in the case of contact by the agency of an intervenient.

Besides, even on this explanation, the mind must have previously been in contact with the object in the entire absence of intervenient; only if that has happened could contact through an intervenient bring knowledge, a knowledge by way of memory, and, even more emphatically, by way of reasoned comparison [ending in identification]: but this process of memory and comparison is excluded by the theory of first knowledge through the agency of a medium.

Finally, we may be told that the impinging light is modified by the thing to be seen and so becomes able to present something perceptible before the visual organ; but this simply brings us back to the theory of an intervenient changed midway by the object, an explanation whose difficulties we have already indicated.

5. But some doubt arises when we consider the phenomena of hearing.

Perhaps we are to understand the process thus: the air is modified by the first movement; layer by layer it is successively acted upon by the object causing the sound: it finally impinges in that modified form upon the sense, the entire progression being governed by the fact that all the air from starting point to hearing point is similarly affected.

Perhaps, on the other hand, the intervenient is modified only by the accident of its midway position, so that, failing any intervenient, whatsoever sound two bodies in clash might make would impinge without medium upon our sense?

Still air is necessary; there could be no sound in the absence of the air set vibrating in the first movement, however different be the case with the intervenient from that onwards to the perception point.

The air would thus appear to be the dominant in the production of sound: two bodies would clash without even an incipient sound, but that the air, struck in their rapid meeting and hurled outward, passes on the movement successively till it reaches the ears and the sense of hearing.

But if the determinant is the air, and the impression is simply of air-movements, what accounts for the differences among voices and other sounds? The sound of bronze against bronze is different from that of bronze against some other substance: and so on; the air and its vibration remain the one thing, yet the difference in sounds is much more than a matter of greater or less intensity.

If we decide that sound is caused by a percussion upon the air, then obviously nothing turning upon the distinctive nature of air is in question: it sounds at a moment in which it is simply a solid body, until [by its distinctive character] it is sent pulsing outwards: thus air in itself is not essential to the production of sound; all is done by clashing solids as they meet and that percussion, reaching the sense, is the sound. This is shown also by the sounds formed within living beings not in air but by the friction of parts; for example, the grinding of teeth and the crunching of bones against each other in the bending of the body, cases in which the air does not intervene.

But all this may now be left over; we are brought to the same conclusion as in the case of sight; the phenomena of hearing arise similarly in a certain co-sensitiveness inherent in a living whole.

6. We return, then, to the question whether there could be light if there were no air, the sun illuminating corporeal surfaces across an intermediate void which, as things are, takes the light accidentally by the mere fact of being in the path. Supposing air to be the cause of the rest of things being thus affected, the substantial existence of light is due to the air; light becomes a modification of the air, and of course if the thing to be modified did not exist neither could be modification.

The fact is that primarily light is no appanage of air, and does not depend upon the existence of air: it belongs to every fiery and shining body, it constitutes even the gleaming surface of certain stones.

Now if, thus, it enters into other substances from something gleaming, could it exist in the absence of its container?

There is a distinction to be made: if it is a quality, some quality of some substance, then light, equally with other qualities, will need a body in which to lodge: if, on the contrary, it is an activity rising from something else, we can surely conceive it existing, though there be no neighbouring body but, if that is possible, a blank void which it will overleap and so appear on the further side: it is powerful, and may very well pass over unhelped. If it were of a nature to fall, nothing would keep it up, certainly not the air or anything that takes its light; there is no reason why they should draw the light from its source and speed it onwards.

Light is not an accidental to something else, requiring therefore to be lodged in a base; nor is it a modification, demanding a base in which the modification occurs: if this were so, it would vanish when the object or substance disappeared; but it does not; it strikes onward; so, too [requiring neither air nor object] it would always have its movement.

But movement, where?

Is space, pure and simple, all that is necessary?

With unchecked motion of the light outward, the material sun will be losing its energy, for the light is its expression.

Perhaps; and [from this untenable consequence] we may gather that the light never was an appanage of anything, but is the expressive Act proceeding from a base [the sun] but not seeking to enter into a base, though having some operation upon any base that may be present.

Life is also an Act, the Act of the soul, and it remains so when anything -- the human body, for instance -- comes in its path to be affected by it; and it is equally an Act though there be nothing for it to modify: surely this may be true of light, one of the Acts of whatever luminary source there be [i.e., light, affecting things, may be quite independent of them and require no medium, air or other]. Certainly light is not brought into being by the dark thing, air, which on the contrary tends to gloom it over with some touch of earth so that it is no longer the brilliant reality: as reasonable to talk of some substance being sweet because it is mixed with something bitter.

If we are told that light is a mode of the air, we answer that this would necessarily imply that the air itself is changed to produce the new mode; in other words, its characteristic darkness must change into non-darkness; but we know that the air maintains its character, in no wise affected: the modification of a thing is an experience within that thing itself: light therefore is not a modification of the air, but a self-existent in whose path the air happens to be present.

On this point we need dwell no longer; but there remains still a question.

7. Our investigation may be furthered by enquiring: Whether light finally perishes or simply returns to its source.

If it be a thing requiring to be caught and kept, domiciled within a recipient, we might think of it finally passing out of existence: if it be an Act not flowing out and away -- but in circuit, with more of it within than is in outward progress from the luminary of which it is the Act -- then it will not cease to exist as long as that centre is in being. And as the luminary moves, the light will reach new points -- not in virtue of any change of course in or out or around, but simply because the act of the luminary exists and where there is no impediment is effective. Even if the distance of the sun from us were far greater than it is, the light would be continuous all that further way, as long as nothing checked or blocked it in the interval.

We distinguish two forms of activity; one is gathered within the luminary and is comparable to the life of the shining body; this is the vaster and is, as it were, the foundation or wellspring of all the act; the other lies next to the surface, the outer image of the inner content, a secondary activity though inseparable from the former. For every existent has an Act which is in its likeness: as long as the one exists, so does the other; yet while the original is stationary the activity reaches forth, in some things over a wide range, in others less far. There are weak and faint activities, and there are some, even, that do not appear; but there are also things whose activities are great and far-going; in the case of these the activity must be thought of as being lodged, both in the active and powerful source and in the point at which it settles. This may be observed in the case of an animal's eyes where the pupils gleam: they have a light which shows outside the orbs. Again there are living things which have an inner fire that in darkness shines out when they expand themselves and ceases to ray outward when they contract: the fire has not perished; it is a mere matter of it being rayed out or not.

But has the light gone inward?

No: it is simply no longer on the outside because the fire [of which it is the activity] is no longer outward going but has withdrawn towards the centre.

But surely the light has gone inward too?

No: only the fire, and when that goes inward the surface consists only of the non-luminous body; the fire can no longer act towards the outer.

The light, then, raying from bodies is an outgoing activity of a luminous body; the light within luminous bodies -- understand; such as are primarily luminous -- is the essential being embraced under the idea of that body. When such a body is brought into association with Matter, its activity produces colour: when there is no such association, it does not give colour -- it gives merely an incipient on which colour might be formed -- for it belongs to another being [primal light] with which it retains its link, unable to desert from it, or from its [inner] activity.

And light is incorporeal even when it is the light of a body; there is therefore no question, strictly speaking, of its withdrawal or of its being present -- these terms do not apply to its modes -- and its essential existence is to be an activity. As an example: the image upon a mirror may be described as an activity exercised by the reflected object upon the potential recipient: there is no outgoing from the object [or ingoing into the reflecting body]; it is simply that, as long as the object stands there, the image also is visible, in the form of colour shaped to a certain pattern, and when the object is not there, the reflecting surface no longer holds what it held when the conditions were favourable.

So it is with the soul considered as the activity of another and prior soul: as long as that prior retains its place, its next, which is its activity, abides.

But what of a soul which is not an activity but the derivative of an activity -- as we maintained the life-principle domiciled in the body to be -- is its presence similar to that of the light caught and held in material things?

No; for in those things the colour is due to an actual intermixture of the active element [the light being alloyed with Matter]; whereas the life-principle of the body is something that holds from another soul closely present to it.

But when the body perishes -- by the fact that nothing without part in soul can continue in being -- when the body is perishing, no longer supported by that primal life-giving soul, or by the presence of any secondary phase of it, it is clear that the life-principle can no longer remain; but does this mean that the life perishes?

No; not even it; for it, too, is an image of that first out-shining; it is merely no longer where it was.

8. Imagine that beyond the heavenly system there existed some solid mass, and that from this sphere there was directed to it a vision utterly unimpeded and unrestricted: it is a question whether that solid form could be perceived by what has no sympathetic relation with it, since we have held that sympathetic relation comes about in virtue of the nature inherent in some one living being.

Obviously, if the sympathetic relationship depends upon the fact that percipients and things perceived are all members of one living being, no acts of perception could take place: that far body could be known only if it were a member of this living universe of ours -- which condition being met, it certainly would be. But what if, without being thus in membership, it were a corporeal entity, exhibiting light and colour and the qualities by which we perceive things, and belonging to the same ideal category as the organ of vision?

If our supposition [of perception by sympathy] is true, there would still be no perception -- though we may be told that the hypothesis is clearly untenable since there is absurdity in supposing that sight can fail in grasping an illuminated object lying before it, and that the other senses in the presence of their particular objects remain unresponsive.

[The following passage, to nearly the end, is offered tentatively as a possible help to the interpretation of an obscure and corrupt place.]

[But why does such a failing appear impossible to us? We answer, because here and now in all the act and experience of our senses, we are within a unity, and members of it. What the conditions would be otherwise, remains to be considered: if living sympathy suffices the theory is established; if not, there are other considerations to support it.

That every living being is self-sensitive allows of no doubt; if the universe is a living being, no more need be said; and what is true of the total must be true of the members, as inbound in that one life.

But what if we are invited to accept the theory of knowledge by likeness (rejecting knowledge by the self-sensitiveness of a living unity)?

Awareness must be determined by the nature and character of the living being in which it occurs; perception, then, means that the likeness demanded by the hypothesis is within this self-identical living being (and not in the object) -- for the organ by which the perception takes place is in the likeness of the living being (is merely the agent adequately expressing the nature of the living being): thus perception is reduced to a mental awareness by means of organs akin to the object.

If, then, something that is a living whole perceives not its own content but things like to its content, it must perceive them under the conditions of that living whole; this means that, in so far as it has perception, the objects appear not as its content but as related to its content.

And the objects are thus perceived as related because the mind itself has related them in order to make them amenable to its handling: in other words the causative soul or mind in that other sphere is utterly alien, and the things there, supposed to be related to the content of this living whole, can be nothing to our minds.]

This absurdity shows that the hypothesis contains a contradiction which naturally leads to untenable results. In fact, under one and the same heading, it presents mind and no mind, it makes things kin and no kin, it confuses similar and dissimilar: containing these irreconcilable elements, it amounts to no hypothesis at all. At one and the same moment it postulates and denies a soul, it tells of an All that is partial, of a something which is at once distinct and not distinct, of a nothingness which is no nothingness, of a complete thing that is incomplete: the hypothesis therefore must be dismissed; no deduction is possible where a thesis cancels its own propositions.