Thanks silsol. I don't know whether Alexander was the first to talk about the unity of the Holy Trinity or whether Arius was the first to mount a challenge to these views. If this is the case it is remarkable that the trinity concept took 300 years to develop to the extent that a word (trinity) was associated with it.
In any case the concept was firmly established in the 4th century but was not mentioned in scripture. If it had been that important a concept I would have thought that at least Paul would have mentioned and clarified it.
