Classical Christian orthodoxy insists that God is Triune: there is only one God, and this God is Father, Son, and Holy Spirit. The Niceno-Constantinopolitan Creed (381) states that the Father and Son arehomoousios (of one substance). The Athanasian Creed expresses this central Christian conviction starkly: “So the Father is God, the Son is God, and the Holy Spirit is God; and yet they are not three Gods, but one God.” Belief in both the distinctness and the divinity of the persons, on one hand, and belief in the oneness or unity of God, on the other hand, are essential to orthodox Christian belief. But what does this really mean? And how could it possibly be true?
What theologians sometimes refer to as the “threeness–oneness problem of the Trinity,” and what philosophers call the “logical problem of the Trinity” is well-known. It arises from the conjunction of three central tenets of the doctrine:
(T1) There is exactly one God.
(T2) Father, Son, and Holy Spirit are not identical.
(T3) Father, Son, and Holy Spirit are consubstantial.
The logical problem is that the conjunction of T1–T3 appears to be flatly inconsistent. This problem may be expressed as follows:
(LPT1) There is exactly one God, the Father Almighty (from T1).
(LPT2) The Father is God (from LPT1).
(LPT3) The Son is consubstantial with but not identical to the Father (from T2 and T3).
(LPT4) If there are x and y such that x is a God, x is not identical to y, and y is consubstantial withx, then it is not the case that there is exactly one God (premise).
(LPT5) Therefore: It is not the case that there is exactly one God (from LPT2, LPT3, and LPT4).
[Thomas McCall, Michael Rea, Philosophical and Theological Essays on the Trinity (2010, Oxford University Press)]
What theologians sometimes refer to as the “threeness–oneness problem of the Trinity,” and what philosophers call the “logical problem of the Trinity” is well-known. It arises from the conjunction of three central tenets of the doctrine:
(T1) There is exactly one God.
(T2) Father, Son, and Holy Spirit are not identical.
(T3) Father, Son, and Holy Spirit are consubstantial.
The logical problem is that the conjunction of T1–T3 appears to be flatly inconsistent. This problem may be expressed as follows:
(LPT1) There is exactly one God, the Father Almighty (from T1).
(LPT2) The Father is God (from LPT1).
(LPT3) The Son is consubstantial with but not identical to the Father (from T2 and T3).
(LPT4) If there are x and y such that x is a God, x is not identical to y, and y is consubstantial withx, then it is not the case that there is exactly one God (premise).
(LPT5) Therefore: It is not the case that there is exactly one God (from LPT2, LPT3, and LPT4).
[Thomas McCall, Michael Rea, Philosophical and Theological Essays on the Trinity (2010, Oxford University Press)]