John Calvin Commentary Ephesians 5:13

"But all things when they are reproved are made manifest by the light: for everything that is made manifest is light." — Ephesians 5:13 (ASV)

But when all things are reproved. As the participle (φανερούμενον), which is translated that which does make manifest, is in the middle voice, it admits either of a passive or active meaning. It may be either rendered that which is made manifest, or that which does make manifest. If the passive meaning, which is followed by the ancient translator, is preferred, the word light will denote, as previously, that which gives light. The meaning will then be that evil works, which had been concealed, will stand out to public view when they have been made manifest by the word of God. If the participle is taken actively, there will still be two ways of explaining it:

1. Whatever manifests is light.
2. That which manifests anything or all things is light, taking the singular as used for the plural number.

There is no difficulty, as Erasmus dreaded, about the article, for the apostles do not typically adhere very strictly to rule about placing every article, and even among elegant writers, this way of using it would be allowable.

The context appears to me to show clearly that this is Paul’s meaning. He had exhorted them to reprove the evil works of unbelievers and thus to drag them out of darkness; and he now adds that what he instructs them to do is the proper business of light—to make manifest. It is Light, he says, which makes all things manifest; consequently, it followed that they were unworthy of the name if they did not bring to light what was involved in darkness.