If at this point in our discussion we revert once more to the realm of physical manifestations of light, dealt with in the preceding chapters, we do so because by studying them in the present context we shall gain further insight into the fact that one plane of nature provides illustrations of processes which on another plane remain more or less veiled. At the same time this will help us to learn more about the properties of levity-space. The optical phenomenon which we shall discuss in this sense is that of the so-called pin-hole camera. (The pin-hole camera effect is easily produced by a keyhole in a closed door which on one side faces a window and on the other leads to a comparatively dark room.)
The usual explanation of the appearance of the optical image on the back inside wall of such a camera is that light-rays, emanating from every point outside, cross each other in the aperture of the camera and so - again point by point - create the inverted image. No such explanation, clearly, is open to us. For the world of external objects is a whole, and so is its image appearing in the camera. Equally, the light entering the camera is not a sum of single rays. Pure observation leads to the following description of the optical process.
By surveying the path which the light takes from the illuminated surface of the outer objects via the pin-hole to the optical image inside the camera, we realize that the light-realm engaged in this process has the shape of a double cone, with its apex in the opening of the camera. Within this cone the light carries the image across the space stretching in front of the light-reflecting objects up to the point where the image becomes visible by being caught on the back wall of the camera.
Thus in every section of the cone the image is present in its totality - even in the very apex of the cone. There, too, the image in all its details is present as a whole, though without (ideally) any spatial extension. Seen thus, on this level of its action the light-ether reveals as one of its characteristics the faculty of making present in a spaceless point an image originally expanded in space, and of letting it emerge from this point in spatial expansion.
Further, there is the fact that, wherever we set up a pin-hole camera, the aperture in its front will cause the formation of an optical image inside it. This shows that each point in space filled with light is the bearer of an optical image, contracted to a point, of the entire world of light-reflecting objects surrounding it. All we do with such a camera is to select a particular image and bring it to separate visibility.
Through these observations we grow aware of light's faculty of communicating simultaneously to space as a whole, and to each point in it, a potential image of the light-reflecting object.
What we observe here in the sphere of physical light-activity is exactly what the light-ether performs on a higher level of nature when with its help the spiritual archetype of a plant takes on spatial appearance. For to this end the archetype, itself without spatial limitations, imprints its image into the tiny seed, whence the growing plant organism carries it again into space. And there is in principle no limitation to the number of such seeds, each of which will bear the complete image of the archetype.
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(d) SOUND
The characteristics of the third modification of ether are such that they prompted Rudolf Steiner to give it as a second name, besides chemical ether, that of sound-ether. In view of the fact, stressed at the beginning of this chapter, that perception of the ether is achieved by a heightening of the power of the spirit-eye, it must cause surprise to learn that a certain mode of activity of the ether has a quality which makes appeal to aural experiences. The full answer to this riddle must await the discussion that follows this chapter. Two points, however, may be brought forward at once. Firstly, where gravity, with its tendency to individualize, is absent, no such sharp distinctions exist between one form of perception and another as are found in the sphere of the physical senses.6 Secondly, even in ordinary sense-perception a certain overlapping of visual and aural experiences is known to us. We need only think how common it is to give musical attributes, such as 'consonant' and 'dissonant' to colours, and to describe tones as 'light' and 'dark'. The reason is that subconsciously we accompany visual experiences with tone-sensations, and vice versa. Cases are even known of human beings in whom the secondary sensation occurs with such intensity as to equal the primary one. Such people say that they 'see' sounds and 'hear' colours.