I believe the council of Nicea was convened after an apostasy took root in the Christian faith following the death of the apostles. By that time, 325 C.E., apostate notions had infiltrated, just as the Bible foretold. (2 Thessalonians 2:3,4) It is not that the Bible is unclear, but rather the unscriptural lies taught by those described in the Bible as "oppressive wolves [that] will enter in among you and will not treat the flock with tenderness, and from among you yourselves men will rise and speak twisted things to draw away the disciples after themselves." (Acts 20:29,30)