“Seth material” search engine (Jane Roberts)

The quality called light on this plane could just as well appear as sound in another; and for that matter, even on this plane, light can be changed into sound, and sound into light. It is always interaction which is important. Even the mental enzymes themselves are interchangeable, as far as the principle behind them is concerned, though for practical purposes they maintain separate and distinct qualities in their materializations in one plane.

That is why it is possible for some human beings to experience sound as color or to see color as sound. Granted, this is not a characteristic experience, but if the mental enzymes were not interchangeable in principle, then the experience would not be possible. Light would never be heard, for example, and sound would never be seen.

In practical terms, these mental enzymes must — and do — give a predictable, more or less dependable, result. The thing to remember, though, is that this interchangeability can occur, and is, therefore, a property of mental enzymes in general. … On your plane, the action of these mental enzymes appear to be more or less inflexible, static, irreversible and permanent. Of course, this is not the case. …