Athanasius argues that “Father” is preferable to the Arian “Unoriginate” as a name for the First Person.  It is more Scriptural, and it also names the First Person by reference to God the Son rather than by reference to the creation.

Plus, “Father” is the liturgical name for the First Person: “when He teaches us to pray, He says not, ‘When you pray, say, O God Unoriginate,’ but rather, ‘When you pray, say, Our Father, which art in heaven.’ And it was His will that the Summary of our faith should have the same bearing, in bidding us be baptized, not into the name of Unoriginate and originate, nor into the name of Creator and creature, but into the Name of Father, Son, and Holy Ghost. For with such an initiation we too, being numbered among works, are made sons, and using the name of the Father, acknowledge from that name the Word also in the Father Himself.”

Athanasius’ lex orandi argument cuts in more than one direction: It not only chips away at Arianism, but it also assaults any sacramental theology that denies or hedges the efficacy of baptism.  If we are baptized into the name of the Father, doesn’t that mean, as Athanasius says, that we are “made sons”?  If we are not made sons, why are we bearing the Father’s name?