Jamieson, Fausset and Brown on 1 Corinthians 11:19

19. heresies--Not merely "schisms" or "divisions" (1Co 11:18), which are "recent dissensions of the congregation through differences of opinion" [Augustine, Con. Crescon. Don. 2.7, quoted by Trench, Greek Synonyms of the New Testament], but also "heresies," that is, "schisms which have now become inveterate"; "Sects" [Campbell, vol. 2, pp. 126, 127]: so Ac 5:17; 15:5 translate the same Greek. At present there were dissensions at the love-feasts; but Paul, remembering Jesus' words (Mt 18:7; 24:10, 12; Lu 17:1) foresees "there must be (come) also" matured separations, and established parties in secession, as separatists. The "must be" arises from sin in professors necessarily bearing its natural fruits: these are overruled by God to the probation of character of both the godly and the ungodly, and to the discipline of the former for glory. "Heresies" had not yet its technical sense ecclesiastically, referring to doctrinal errors: it means confirmed schisms. St. Augustine's rule is a golden rule as regards questions of heresy and catholicity: "In doubtful questions, liberty; in essentials, unity; in all things, charity."

that ... approved may be made manifest--through the disapproved (reprobates) becoming manifested (Lu 2:35; 1Jo 2:19).