What constitutes night to all beings, in that the man of spiritual restraint is awake. Wherein beings are widely awake, the spiritually awakened sees it as night.
Krishna makes a stunning comparison and contrast illustrating the nature and elegance of a spiritual Knower.
Self-delight and sensory thrill are mutually opposite, like light and darkness. The Knower finds the sensory world utterly dark, offering no interest to him. For him the inner domain holds all the brilliance and revelation. But it is utterly dark, invisible to the ordinary folk. Unable to find anything there, they reject it altogether, like darkness. It is impenetrable to them, unlike the outer world.
The Knower traces everything to the mind, intelligence, and all they represent. Mind alone leads all sensory interactions, registering the resulting imprints, and shapes memory and knowledge.
Intelligence sifts all mental data, generates discrimination to guide further interactions. Perception itself is an inner process, without which the outer cannot be.