Jamieson, Fausset and Brown on 1 Corinthians 8:4

4. As concerning, &c.--resuming the subject begun in 1Co 8:1, "As touching," &c.

idol is nothing--has no true being at all, the god it represents is not a living reality. This does not contradict 1Co 10:20, which states that they who worship idols, worship devils; for here it is the Gods believed by the worshippers to be represented by the idols which are denied to have any existence, not the devils which really under the idols delude the worshippers.

none other God--The oldest manuscripts omit the word "other"; which gives a clearer sense.