498. As these "degrees of light" appear as a rising scale and the level of the I's energies – in conformity with the principle of perspective – forms the vantage point from where the other levels can be surveyed, then that first level marks the boundaries of the I's "experience of light", that is to say, its experience of life. All the grades of "light" which lie directly above the level of the I's energies on the scale, will be perceived by the I as a stronger light than that at its own level, while all the grades of "light" which lie directly below that level will be perceived as a weaker "light" than that of its own level. There are thus two kinds of perception. While the degrees of "light" higher on the scale are still perceived as "light", the light at lower levels is perceived, on the other hand, as a contrast. It is this contrast that we express by the term "darkness". And we have here, by virtue of the "principle of perspective", the two contrasts "light" and "darkness" upon which all sensory perception is based. It is this "light" and "darkness" which in its most concentrated physical form is perceived respectively as the two colours "white" and "black". These two sensory impressions thus constitute the borderland of our experience of life. At the point where the sensory ability begins to fail when we are sensing upwards on the "ladder of light", then "matter" appears as "white". And when our senses begin to fail as we look downwards along that same ladder, "matter" gives the impression of being "black". It is between these two forms of experiencing that the I's ability to experience has its territory. Here sensory reactions are stronger and so things are experienced in greater detail. This stronger sensory impression has the effect that, in this sphere, the "steps" on the "ladder of light" do not appear as "light" or "dark" or as "black" or "white", but on the contrary as an experience of all the other existing colours or the actual colour spectrum itself. This scale thus constitutes only that section of the "scale of light" or that step on the "ladder of light" which we are able to perceive in detail with our sensory ability. If we sense downwards along the ladder the first "matter" appearing after the "black" is sensed as identical with the colour spectrum's first colour, the so-called "red" colour. Then come all the other colours of the spectrum in the order previously mentioned, that is: "orange", "yellow", "green", "blue" and ending with "violet". The next colour after "violet" is "white". Things which appear to be colourless, for example glass or other transparent objects, thus belong to the "white" category. In the scale of colours this appearance is, in fact, a shade existing in the "zone of light", and consequently constitutes a grade of "white".