What is darkness?
Is darkness merely a lack of light or is darkness a significant and substantive reality? In the language of the Philosophers, is darkness העדר אור or a מציאות.
The Rambam in his "Moireh" cites the opinion of the school of the מדברים who maintain that darkness is not merely a lack of light but the Rambam differs and contends that it is.
The Heilige Rogochover discusses this question and brings numerous proofs from Chazal that darkness is a metzius.
1] The Yerushalmi [Brachos 6/8] offers a moshol of two servants of the king. One is given the daytime to serve, the other is given the night. In the same vein, light serves during the day while darkness serves at night. From here we see that darkness is a metzius, a substantive reality.
2] There is an argument in the Yerushalmi [Brachos 1/1] when the day starts and when the day ends. According to one opinion it starts at sunset while the other opinion maintains that it starts when the stars come out. One opinion holds that the night ends at dawn while the other opinion holds that it ends at sunrise.
They are arguing about our question. If darkness is a lack of light then as long as there is still light it is day. That is why night starts when three stars appear and it is completely dark but not before. But if darkness is a metzius, then the moment the sun sets and it gets a bit dark, it is already considered night.
The same logic applies to the argument about the end of the night. If darkness is a lack of light then the moment light appears at dawn the day starts and night ends. But if darkness is a metzius then as long as there is any darkness, its שלטון and reign has not ended and it is not yet the time of the "ruling" of the day. That only begins when all of the darkness disappears at sunrise. [I could see one arguing with this logic but I am certain that if the Rogochover would hear my question he would swallow me up alive, so I will keep my question to myself and ask him in the olam ha-emes where things are safe...:-)].
3] In davening we say וגולל אור מפני חושך - Hashem "rolls away" the light before the darkness. This implies that darkness is a metzuis. Hashem has to "bring" the darkness. If it weren't a metzius but just a lack of light, then we could say "וגולל אור" alone, he removes the light and automatically there is darkness.
4] The gemara in Psachim [2a] says that Hashem called the dark and commanded it to appear at night. That implies that it is a metzius and not just a lack of light.
So we learned some philosophy, some Yerushalmi and tasted Torah from the Rogochover Gaon, the most brilliant Rav in a thousand years. Are you glad you came??