Paul Tillich has written that
"...all dogmas were formulated negatively, that is, as reactions against misinterpretations from inside the church... We may call them protective doctrines, for they were intended to protect the substance of the biblical message.. When new doctrines arose which seemed to undercut the fundamental confession, the protective doctrines were added to it.. Since each new protective statement was itself subject to misinterpretation, there was always the need for sharper theoretical formulations. In order to do this it was necessary to use philosophical terms. This is how the many philosophical concepts entered into the Christian dogmas." (Tillich, p xxxviii-xxxix)
Christianity began with faith in what was believed to be a revelation of God. The scripture and tradition (both oral and written) that supported that faith and revelation were in turn believed to be inviolable but both had to be explained.
Since the revelation was connected with the idea of salvation, it is only natural that the original faith be protected. Consequently, while the history of Christian Thought reveals a divergence of views, "protective doctrines" (as Tillich calls them) arose to maintain the accepted confession of faith and to silence "heresies".
The philosophy that joined with Christian faith to explain it was secondary to it in origin and therefore the theological conlusions were given precedence. With such an approach, the necessary metaphysic discussed earlier was not present.
Unity provides the necessary metaphysic because it meets the twofold criteria of beginning with Being and by relating the Christological and Soteriological concerns to a meaningful structure of Human Consciousness without compromising the theological rubric of Salvation.