There are times when it is wise to become invisible. The image is of fresh darkness, the period after sundown when the light has gone. There is still much activity left over from the light of day, and movements in the outer world are at their most dangerous. Even the smallest sound, the faintest glow of light, can attract unwanted attention.
When the darkness of stupidity reigns, it is best that your own brilliance stay "hidden under a bushel basket". That is, your thoughts and efforts should be quiet and self-contained, and protected, as much as possible, from harmful external influences.
