But all things that are reproved are made manifest by the light: for whatsoever doth make manifest is light. But all things that are reproved - Dr. Macknight paraphrases this verse as follows: "Now all these reprovable actions, ελεγχομενα, which are practised in celebrating these mysteries, are made manifest as sinful by the Gospel; and, seeing every thing which discovers the true nature of actions is light, the Gospel, which discovers the evil nature of the actions performed in these mysteries, is light."
The apostle speaks against these mysteries as he speaks against fornication, uncleanness, and covetousness; but by no means either borrows expression or similitude from them to illustrate Divine truths; for, as it would be a shame even to speak of those things, surely it would be an abomination to allude to them in the illustration of the doctrines of the Gospel.