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.