Cyprian

Hence heresies not only have frequently been originated, but continue to be so; while the perverted mind has no peace-while a discordant faithlessness does not maintain unity. But the Lord permits and suffers these things to be, while the choice of one's own liberty remains, so that while the discrimination of truth is testing our hearts and our minds, the sound faith of those that are approved may shine forth with manifest light. The Holy Spirit forewarns and says by the apostle, "It is needful also that there should be heresies, that they which are approved may be made manifest among you." Thus the faithful are approved, thus the perfidious are detected; thus even here, before the day of judgment, the souls of the righteous and of the unrighteous are already divided, and the chaff is separated from the wheat.