354. It results from all this, that light cannot enter unchanged into mutual operation with matter. The tension of æther changes itself in matter. This change of light through the influence of matter is a debilitation of the tension of æther and lastly its complete cessation. There can be therefore no absolutely transparent matter; the æther only is this absolutely transparent matter. The denser a material is, by so much the more will it be capable of suppressing in itself the tension of light. The most transparent bodies must also become with a greater density adiaphanous or opaque, because the Metallic increases in them.
355. This suppression or expiration of the tension of light in bodies has received, as likewise proceeding from the mechanical theory of light, the name of absorption. The absorption is not a mechanical adherence of the particles of light in the pores of bodies. There are no pores for light, and this requires none.
356. The absorption or decrescence of light is a retrogression of light into the indifference of æther, into darkness. Light in conflict with matter does not continue light, but becomes a mean condition between light and darkness.
357. The substratum of light, the æther, has two extreme conditions, and only two, the tensed and the non-tensed; the one is the light, the other the dark. Between the two, however, are the mediate conditions of twilight or "clare-obscure." The light æther emits rays, the dark does not; the mediate conditions are half the two. The light condition is the clear unsullied light, the absolute translucency; the darkness is the absolute want of translucency; the mediate members are offuscated light, mediate tensions of æther.
358. The mean tension of æther, or light mingled with darkness, is called Colour. Colour is a finite, fixed light, the actual transmission of light into matter.
359. No matter can be uncoloured. An uncoloured matter is a nonentity.
360. Since matter is rigidified light, even so must it be posited in reference to colour, like light. Pure light materially substantiated or posited is White. The untensed æther materially posited is Black.
361. The mediate tensions of æther, or the mixture of Light and Dark, are mean conditions of White and Black, mixtures of the two extremes or androgynisms of White and Black. If we do not call White and Black colours, colours are then partial positions of light in matter, or in the dark.
362. Colour originates only in the confinity of Light and Dark, or in the limit between White and Black. They are therefore microscopic.