He therefore began his thinking from the unity of God. The Father is the guarantee of this unity of the monarchy. The Son (Christ) is assigned the second position and the Holy Spirit the third. Tertullian was not thinking of a purely static situation within God, the metaphysical Trinity, but of an economic, organic and dynamic threeness. His idea of unity is not mathematical but philosophical, an organic unity, not an abstract bare point, Father, Son and Spirit are in the one reality of God, For Tertullian, the second and third persons proceed from the unitas substantia because they had a task to fulfill. Only the Father remains completely transcendent.