What caused doctrinal controversies in the Early Church ?

It is difficult to imagine a student approaching the history of the Early Church who would not, at an early stage of his involvement with this subject, be struck by the observation that he is dealing with an age of innumerable controversies. From every new page of any textbook he (or she, for that matter) is greeted by yet another name of yet another conflict that appears to have all but torn apart the Christian community of its time. It must appear that, indeed, those Christians have been quarrelling all the time.