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Plotino - Tratado 29,2 (IV, 5, 2) — Diferentes teses sobre a visão

Enéada IV, 5, 2

sexta-feira 13 de maio de 2022, por Cardoso de Castro

    

Capítulo 1-5: É necessário um intermediário   entre o órgão e o objeto sensível?

  • Cap 1, 1-13: Introdução
  • Cap 1, 13-4 a 4-39: O caso da vista
  • Cap 1, 13-40: Um intermediário não é indispensável quando se explica a vista pela simpatia
  • Cap 2, 1-15: Exame   doxográfico das diferentes teses
  • Cap 3-4: Três maneiras   de fazer da luz um intermediário no caso da visão  . Críticas e conclusão: a afecção   de um intermediário não é a condição da vista
  • Cap 5: A audição  
    

Míguez

2. Si la visión consiste en enlazar la luz del ojo con la luz que se interpone hasta el objeto sensible  , conviene que exista ese intermediario que es la luz, como lo exige la misma hipótesis. Pero si es el objeto, y mejor el cuerpo coloreado, el que produce la alteración, ¿qué es lo que impide que esta modificación llegue inmediatamente al ojo, sin la ayuda de ningún cuerpo intermedio? Y eso, aun en el supuesto de que tengamos ahora ante los ojos un medio que recibe la modificación.

En cuanto a los que admiten que la mirada emana de los ojos, no podrían concluir en absoluto que exista un cuerpo intermedio, de no sentir el temor de que el rayo   visual no caiga. Pero es claro que se trata aquí de un rayo   de luz, y la luz se propaga en línea recta. En cuanto a los que toman como causa   una determinada resistencia, tienen verdadera necesidad de un medio. Los que se inclinan por las imágenes, afirmando que éstas atraviesan el vacío, inquieren la existencia   de un espacio para que las imágenes no se vean detenidas. De modo que, como el obstáculo   se reduce al mínimo cuando no existe un medio, no ponen en duda nuestra hipótesis. Y los que afirman, en fin, que la visión es un acto de simpatía, dirán realmente que se ve menos cuando existe un cierto medio, porque este medio impide, embaraza y hace más oscura la simpatía. Para el caso de que el medio fuese afín a los seres, el resultado que obtendríamos es que la simpatía pierde consistencia al ser paciente el medio mismo. Porque si un cuerpo denso   se ve presa del fuego y quema realmente, sus partes profundas sufrirán menos que sus partes superficiales con la acción del fuego. Si, pues, las partes de un ser animado único simpatizan entre sí, ¿se sentirán menos afectadas de existir entre ellas un medio? Se sentirán, sin duda, menos afectadas, y la impresión que reciban estará atemperada a lo que quiera la naturaleza, ya que el medio impide que esa impresión sea excesiva, salvo, claro es, que la influencia dada sea tal que el medio no resulte afectado enteramente.

Si existe, por tanto, una relación de simpatía entre las partes del ser animado único y si, a la vez, nosotros mismos compartimos esa simpatía, es porque, ciertamente, nos encontramos en un universo   único y formamos también parte de él; de modo que, ¿cómo no admitir una continuidad cuando tenemos la sensación de un objeto lejano? Debe existir, en efecto, un medio continuo, porque el ser animado universal   tiene que ser continuo. Pero este medio sólo debe ser afectado por accidente, ya que en otro caso todo debería ser afectado por todo. Ahora bien, si una cosa concreta es afectada por otra cosa, también muy concreta, no es de todo punto necesario que exista el medio. Habrá que preguntarse por qué se habla de un medio necesario para la visión. Pues parece claro que lo que atraviesa el aire no lo hace siempre sufrir, sino que se limita a dividirlo. Cuando una piedra   cae, por ejemplo, ¿qué otra cosa ocurre al aire sino que no le opone resistencia? No es lógico atribuir la caída de la piedra, completamente natural, a la reacción del aire que tiende a reemplazarla, ya que de la misma manera explicaríamos el movimiento ascendente del fuego, lo cual es absurdo. Porque la procedencia del fuego sobre la fuerza que ejerce el aire se justifica por la rapidez de su movimiento y si se dice que la velocidad de su empuje aumenta con la velocidad del movimiento, entonces el movimiento del fuego se produciría accidentalmente y no habría razón para que se dirigiese a lo alto. Por otra parte, los árboles crecen hacia arriba sin recibir ningún impulso, y nosotros mismos al movernos cortamos el aire, pero no por eso nos detiene su empuje, que se limita únicamente a llenar los vacíos sucesivos que hemos dejado. Por tanto, si el aire resulta dividido por cuerpos en movimiento sin ser afectado por ello, ¿qué impide admitir que las formas visuales pasen a través de él sin que siquiera le dividan? Si es cierto que esas formas no le atraviesan como lo hace la corriente de un río, ¿por qué necesariamente tiene que ser afectado, y nosotros por su intermedio luego de la impresión recibida por él? Si la sensación viniese precedida de una modificación del aire, nosotros no veríamos el objeto al dirigir a él nuestra mirada, sino que sentiríamos tan sólo el aire que se halla a nuestro alcance, como ocurre en la sensación de calor; porque aquí no experimentamos realmente el fuego lejano, sino el aire caliente que está próximo a nosotros. La sensación de que ahora hablamos se produce por contacto, pero no así la que tiene lugar por la vista. De ahí que un objeto no se haga visible colocándolo sobre los ojos, sino que es necesario iluminar el medio, porque el aire, por sí mismo  , es oscuro. Si no fuese oscuro, tal vez no habría necesidad de iluminarlo, pero la oscuridad constituye un obstáculo para la visión y debe ser dominada por la luz. No vemos en realidad un objeto muy próximo a nuestros ojos porque trae consigo la sombra del aire y la suya propia.

Bouillet

II. Si [comme l’enseigne Platon  ] la vision suppose l’union de la lumière   de l’œil avec la lumière interposée jusqu’à l’objet sensible (09), le milieu interposé est la 411 lumière, et ce milieu est nécessaire dans cette hypothèse. Si [comme l’enseigne Aristote  ] la substance colorée produit une modification (τροπή) dans le milieu, qui empêche que cette modification ne parvienne immédiatement à l’œil, même quand il n’y a pas de milieu ? Car, dans ce cas, le milieu interposé est nécessairement modifié avant l’œil. Ceux qui enseignent [comme le font les Platoniciens] que la vision s’opère par une effusion de la lumière de l’œil n’ont aucune raison de supposer un milieu, à moins qu’ils ne craignent que le rayon visuel ne s’égare ; mais ce rayon est lumineux, et la lumière se propage en ligne droite. Ceux qui [comme les Stoïciens] expliquent la vision par la résistance qu’éprouvé le rayon visuel (ἔστασις) ont besoin d’un milieu (10). Les partisans des images (εἴδωλα), soutenant 412 [comme le font les Atomistes (11)] qu’elles se meuvent dans le vide, supposent qu’il y a un espace libre afin que les images ne soient pas arrêtées; par conséquent, comme elles seront d’autant moins arrêtées qu’il n’y aura pas de milieu, cette opinion n’est pas contraire à notre hypothèse.

Quant à ceux qui pensent que la vision s’opère par sympathie (12), ils diront que l’on voit moins bien quand il y a un milieu, parce que ce milieu empêche, entrave et affaiblit la sympathie. Dans ce cas, en effet, le milieu eût-il la même nature et fût-il affecté de la même manière, il affaiblit nécessairement la sympathie. Il se passe alors la même chose que pour un corps qui est profondément brûlé par le feu qu’on en approche : les parties intérieures sont moins affectées, parce qu’elles sont protégées par les parties extérieures. Mais, si les parties d’un seul et même animal   éprouvent des affections sympathiques, seront-elles moins affectées parce qu’il y a un milieu? Oui, sans doute. L’affection sera affaiblie, selon la nature du milieu, parce que ce milieu empêche toute affection excessive, à moins que ce qui est transmis [par une partie à une autre] ne soit tel que le milieu ne puisse en être affecté. Mais, si l’univers est sympathique à lui-même parce qu’il constitue un animal un, et si nous sommes affectés parce que nous sommes contenus dans cet animal un et que nous en formons des parties, pourquoi ne serait-il pas nécessaire qu’il y ait continuité pour que nous sentions un objet éloigné? Il est nécessaire qu’il y ait continuité et qu’il existe un milieu, parce que l’animal un doit être continu; seulement, le continu [le milieu] n’est affecté que par accident; sinon, il faudrait admettre que tout peut être affecté par tout. Mais, si tel être est affecté par tel 413 autre d’une manière, si celui-ci est affecté par celui-là d’une autre manière, il n’y a pas toujours besoin d’un milieu. Si l’on prétend qu’il est besoin d’un milieu pour la vision, il faut en dire la cause : car ce qui traverse l’air ne l’affecte pas toujours et se borne souvent à le diviser. Ainsi, quand une pierre tombe, la seule chose qui arrive à l’air, c’est de ne pas soutenir la pierre : car, puisqu’il est dans la nature de la pierre de tomber, il n’est pas raisonnable de dire qu’elle tombe par la réaction qu’exercé l’air ambiant ; sinon, il faudrait dire que c’est la réaction de l’air ambiant qui fait monter le feu, ce qui est absurde, parce que le feu, par la rapidité de son mouvement, prévient cette réaction. Si l’on dit que la réaction est accélérée par la rapidité même du mouvement, cela arrive par accident et n’a pas de rapport avec l’impulsion de bas en haut : car les arbres croissent par le haut sans recevoir d’impulsion. Nous-mêmes, en marchant, nous divisons l’air, sans que la réaction de l’air nous pousse : l’air qui est derrière nous se borne à remplir le vide que nous avons fait. Si donc l’air se laisse diviser par les corps sans en être affecté, qui empêche qu’il laisse arriver les images à l’œil sans être divisé?

Si ces images ne nous arrivent pas par une espèce d’écoulement ((ροῇ) ,pourquoi l’air serait-il affecté et pourquoi ne serions-nous affectés nous-mêmes que par suite de l’affection que l’air aurait éprouvée? Si nous ne sentions que parce que l’air serait affecté avant nous, nous rapporterions la sensation de la vue, non à l’objet visible, mais à l’air placé près de nous, comme cela a lieu pour la chaleur. Dans ce cas, ce n’est pas le feu éloigné, c’est l’air placé près de nous qui, étant échauffé , nous échauffe nous-mêmes : car la sensation de la chaleur suppose contact, ce qui n’a pas lieu pour la vue. Si l’on voit, ce n’est pas parce que l’objet sensible est placé sur l’oeil [mais parce que le milieu est éclairé] ; or il est nécessaire que le milieu soit éclairé parce que l’air est ténébreux par lui-même. L’air 414 n’aurait pas besoin de lumière s’il n’était pas ténébreux : car [pour que la vision ait lieu], il faut que les ténèbres, qui font obstacle à la vision, soient vaincues par la lumière. C’est peut-être pour cette raison qu’un objet placé très près de l’œil n’est pas vu : car il apporte avec lui l’ombre de l’air et la sienne propre.

Guthrie

NECESSITY OF A MEDIUM   IN THE THEORIES OF VARIOUS PHILOSOPHERS.

2. If vision presupposes the union of the «light of the eye,» with the light interposed (between the eye) and the sense-object itself, the interposed medium is the light, and this medium is necessary, on this hypothesis  . (On the theory of Aristotle) the colored substance produces a modification in the medium; but nothing here would hinder this modification from reaching the eye itself, even when there is no medium. For, in this case, the medium is necessarily modified before the eye is. (The Platonic philosophers) teach that vision operates by an effusion of the light of the eye. They have no need to postulate a medium, unless indeed they should fear that the ray of the eye should lose its way; but this ray is luminous, and the light travels in a straight line. (The Stoics) explain vision by the resistance experienced by the visual ray. They cannot do without a medium. (The Atomists and) the believers in «images» (such as Epicurus  ), insist that these images move in emptiness, thereby implying the existence of a free space to avoid hindering the images. Consequently as they will be hindered in a direct ratio to the existence of a medium, this opinion does not run counter to our own hypothesis (that there is no medium).

A COSMOLOGICAL MEDIUM IS NECESSARY, BUT IT AFFECTS SIGHT ONLY ACCIDENTALLY.

Those who (with Plotinos   himself) teach that vision operates by sympathy, assert that vision is poorer through a medium, because this medium hinders, fetters, and weakens sympathy. In this case, indeed, the medium necessarily weakens sympathy even though it shared the same nature (as the eye and the object), and was affected in the same manner. (It acts like the integument) of some body that is deeply burned by fire applied to it; the interior parts are less affected because they are protected by the exterior parts. There is no doubt that the parts of one and the same animal will be less affected in experiencing sympathy because of the existence of a medium. The affection will be weakened according to the nature of the medium, because such a medium would hinder excess of affection, unless indeed that which is transmitted (by one part to another) is not such as to fail to affect the medium. But if the universe sympathize with itself because it constitutes a single organism, and if we are affected because we are contained within this single organism, and form part of it, why should any continuity be necessary for us to feel a distant object? The single organism, indeed, could not be continuous without the continuity of some medium; this continuous medium is affected only by accident; but otherwise we would have to admit that all can be affected by all. But if these two objects are affected in one manner, and other two objects are affected in another manner, there might not always be need of a medium. Whoever asserts the need of a medium for vision will have to advance a very good argument, inasmuch as that which traverses the air does not always affect the air, and often limits itself to dividing the air. Thus when a stone falls the only thing that happens to the air is that it fails to support the stone. As falling is part of the stone’s nature, it would be unreasonable to assert that its falling was due to the reaction exerted by the ambient air. Otherwise we would have to assert that it is this same reaction of the ambient air that makes fire ascend, which is absurd; because the fire, by the rapidity of its motion, forestalls this reaction. That, by the very rapidity of the motion, reaction is accelerated, takes place only by accident, and has no relation to the upward impulsion; for trees grow from above without receiving any (upward) impulsion. Even we, when walking, divide the air without being pushed by the reaction of the air; the air behind us limits itself to filling the void we have created. If then the air allow itself to be divided by bodies without being affected by them, what would hinder the air from permitting free transit for the images to reach the eye, without being thereby divided?

IMAGES DO NOT REACH US BY EFFLUENCE.

If these images do not reach us by some sort of effluence, why should the air be affected, and why should we ourselves be affected only as a result of the affection experienced by the air ? If we felt only because the air had been affected before us, we would attribute the sensation of sight not to the visible object, but to the air located near us, as occurs with heat. In the latter case it is not the distant fire, but the air located near us which, being heated, then warms us; for the sensation of heat presupposes contact, which does not occur with vision. We see, not because the sense-object is imposed on the eye (but because the medium is illuminated); now it is necessary for the medium to be illuminated because the air by itself is dark. If the air were not dark, it would have no need of light; for (to effectuate vision) the obscurity, which forms an obstacle to vision, must be overcome by light. That is perhaps the reason why an object placed very near the eye is not seen; for it brings with it the darkness of the air, together with its own.

MacKenna

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.