Again, I write a new commandment to you, which is true in him and in you; because the darkness is passing away, and the true light already shines.
Because the darkness is past. The present time is here instead of the past; for he means, that as soon as Christ brings light, we have the full brightness of knowledge: not that every one of the faithful becomes wise the first day as much as he ought to be, (for even Paul testifies that he labored to apprehend what he had not apprehended, (Philippians 3:12,) but that the knowledge of Christ alone is sufficient to dissipate darkness. Hence, daily progress is necessary; and the faith of every one has its dawn before it reaches the noonday. But as God continues the inculcation of the same doctrine, in which he bids us to make advances, the knowledge of the Gospel is justly said to be the true light, when Christ, the Sun of righteousness, shines. Thus the way is shut up against the audacity of those men who try to corrupt the purity of the Gospel by their own fictions; and we may safely denounce an anathema on the whole theology of the Pope, for it wholly obscures the true light. 