...the Trinity is so deeply written into the language and liturgical use of the church that Christians can hardly escape it altogether. Drawing on Jesus's commission in Matthew 28:19, Christian communities, as far back as we know, have normally baptized members "in the name of the Father, and the Son, and the Holy Spirit" as an immersion into the divine power that underlies both Jesus's commands and his promise always to be present with his disciples. Since the beginning of Christian records, liturgical forms of blessing and doxologies at the conclusion of homilies have invoked God's favor and praised God's glory with this characteristic, yet intractably puzzling formulation For some contemporary Christians, trinitarian formulations seems inappropriate because they do not feature the "inclusive language" we want to use for God; for others, they are simply unintelligible. Do we really need them?
Theoretical models of the Trinity, however, whether ancient or modern, always seemed doomed to failure if they are taken to be models for rational explanation-- for actually making some sense of how we can confess the Father, the Son, and Holy Spirit, whom Christians invoke in liturgy and prayer, to be at the same time both radically one and simply and irreducibly three. The reason, of course, is that our thoughts and speech about God as Trinity is not, in any sense, a theory or hypothesis intended to explain how God has touched us in history. So trinitarian language always resists further explanation; it simply confesses, proclaims. And the reason is that the Trinity is not a theory so much as a summary of biblical faith, the briefest and most lapidary of Christian Creeds.
But the relationship of these three remain mysterious as well as crucially important for salvation; their unity remains as central to their divine identity as their distinction.
Khaled Anatolios, Retrieving Nicaea: The Development and Meaning of Trinitarian Doctrine, pp. ix, x, xii..