Philosophical and Theological Essays on the TrinityClassical Christian orthodoxy insists that God is Triune: there is only one God, but there are three divine Persons Father, Son, and Holy Spirit who are somehow of one substance with one another. But what does this doctrine mean? How can we coherently believe that there is only one God if we also believe that there are three divine Persons? This problem, sometimes called the 'threeness oneness problem' or the 'logical problem of the Trinity', is the