and irenaeus was trying to unify those who were left.frustrated him is that they didn't all believe the same thing. they didn't all gather under one kind of leadership. and he, like others, was deeply aware of the dangers of fragmentation. >> narrator: irenaeus thundered against those he saw as heretics, including the so- called gnostics. >> ( dramatized ): let those persons who blaspheme the creator, as do all the falsely so-called gnostics, be recognized as agents of satan by all who worship god. >> bishop irenaeus coined the term we call "orthodox." now, literally in greek, "orthodox" means "straight thinking." it's like "orthodontia" means "straight teeth." i mean, "orthodox" means "straight ideas." and those who didn't agree with his ideas, he called "heterodox"-- that means simply thinking otherwise-- or "heretics," which means people who make choices about what to think. irenaeus didn't want people making choices, he wanted them thinking what the bishop told them to think. >> narrator: irenaeus had to contend, not only with those