Charles Ellicott Commentary 1 Corinthians 8:4

"Concerning therefore the eating of things sacrificed to idols, we know that no idol is [anything] in the world, and that there is no God but one." — 1 Corinthians 8:4 (ASV)

As concerning therefore the eating of those things. See 1 Corinthians 8:1. The subject is resumed after the parenthesis. We have, perhaps, in this repetition of the words a characteristic of a letter written by another from the author’s dictation, as was the case with this and other epistles.

An idol is nothing in the world.: It is nothing in itself but a piece of wood or metal, and it really represents nothing, for we know that there is no God but one. The word “other” was inserted in later manuscripts, probably from a recollection of the words of the first commandment.