16 Even on the plea of promoting unity it is not allowed to dissemble one single dogma; for, as the Patriarch of Alexandria warns us, 'although the desire of peace is a noble and excellent thing, yet we must not for its sake neglect the virtue of loyalty in Christ.' Consequently, the much desired return of erring sons to true and genuine unity in Christ will not be furthered by exclusive concentration on those doctrines which all, or most, communities glorying in the Christian name accept in common. The only successful method will be that which bases harmony and agreement among Christ's faithful ones upon all the truths, and the whole of the truths, which God has revealed.
Source: Orientalis Ecclesiae (Vatican.va)