Our eyes see an object by responding to the vibrations of light that are given off by the object. The light by which we see is white light, which comes from the sun. If we interpose a prism of glass in the way of white light, the particles of glass break up the light into its constituent vibrations. Our eyes pick up on seven of these vibrations, translating them into the colors: red, orange, yellow, green, blue, indigo and violet.
However, if we put a burning-glass at the infrared end of the spectrum and a piece of phosphorus where the rays of the lens converge, the phosphorus will be set on fire by the heat, which means there are vibrations producing heat at that end of the spectrum that our eyes cannot translate into color.
Similarly, if we place a disc or screen at the ultraviolet end of the spectrum, the disc will begin to glow, owing to the effect of the ultraviolet rays that we also cannot see. If we could see these infrared and ultraviolet rays, we would be aware of the objects surrounding us as having new colors and new shades.
Our sense of sound is similarly limited—there are sounds both too high and too low for us to hear.
Infrared and ultraviolet rays do not translate into color in our consciousness because we do not have the faculty of responding to their vibrations. If we did have that faculty, we would be able to ‘see’ more of the real world surrounding us than we currently do. We are surrounded by vibrations that we cannot respond to, vibrations from the invisible worlds. These worlds become visible when we acquire the faculty to respond to their vibrations.
In this sense, the principle of clairvoyance is exactly the same as the principle of ordinary sight.