Not even the churches established in Apostolic times had absolute unity. We should be unified in Spirit and on essentials such as the Oneness of God and
Acts 2:38 being the proper means of conversion. However, how Oneness is understood and the various soteriological aspects of
Acts 2:38 are understood should be open to interpretation and continual study. We can be unified in the Spirit and not legalistically unified on every point of teaching.
If we all understand this, speak this, and stand by this... we are of one mind and speaking the same thing. However, we're allowing unity in diversity and making our differences... a strength.