Albert Barnes Commentary Amos 5:20

"Shall not the day of Jehovah be darkness, and not light? even very dark, and no brightness in it?" — Amos 5:20 (ASV)

Shall not the Day of the Lord be darkness? - He had described that Day as a day of inevitable destruction, such as man’s own conscience and guilty fears anticipate. He then appeals to their own consciences: “Is it not so, as I have said?”

People’s consciences are truer than their intellect. However, they may employ the subtlety of their intellect to dull their conscience; in their heart of hearts, they feel that there is a Judge, that guilt is punished, that they are guilty.

The soul is a witness to its own deathlessness, its own accountability, its own punishability. Intellect carries the question out of itself into the region of conjecture and disputes. Conscience, however, is compelled to receive it back into its own court and to give the sentence, which it would rather withhold.

Like the god of the pagan fable—who changed himself into all sorts of forms but, when he was still held fast, at last gave the true answer—so conscience shrinks back, twists, writhes, evades, turns away. But in the end, it will answer truly when it must.

The prophet then quickly turns upon the conscience and says, “Tell me, for you know.”