Ideas about the Kingdom of the Heavens around us and the unity of believers in Christ within it
Doctrinal disputes, even over such heavy subjects as our relationship to the Law of Moses, can be settled peacefully within the Church, as shown by the Council of Jerusalem in Acts 15.
Heresy is properly defined as divisiveness, not merely believing a false doctrine. Heretics are divisive people. Those who state doctrines with which I disagree, but do so without insisting on division because of my belief, are not heretics. Thus calls for mutual understanding and patience.