Therefore, as to the eating of food offered to idols, we know that “an idol has no real existence,” and that “there is no God but one.”
4. Concerning, therefore, the eating of those things He now returns to the statement with which he had set out, and speaks more plainly in reference to the pretext made use of by the Corinthians. For as the whole of the evil took its rise from this root — that they were pleased with themselves, and despised others, he condemns, in general, that contemptuous knowledge...
In this passage he shows the vanity of idols: As to the eating of things that have been sacrificed to idols, we know that an idol is nothing in the world; or, there is no idol in the world; or, an idol can do nothing in the world: for the form of expression in the original is elliptical.
Commenting on 1 Corinthians 8:4-6
As concerning therefore the eating of those things,.... The apostle having enlarged on the head of knowledge, which those who made an ill use of their Christian liberty urged in favour of their conduct; he returns to the subject in question, in relation to meats, that are offered in sacrifice unto idols.