Early Christian Creeds, J N D Kelly p. 150

(I am not sure exactly what part of this page that T F Torrance was referring to, so my guess is as follows)

. . . On the contrary, that Christ was the Son of God and that, as the Only-begotten, He pre-existed as Son, seems to be the clear implication of the words immediately preceding our clause. We should be on our guard, however, against looking for a Christology in line with the conceptions of later orthodoxy. We have already hinted that the second century father had not altogether made up their minds as to the identity of the Holy Spirit in the incarnation. A view which had considerable currency, and with which the learned theologians felt constrained to harmonise their more sophisticated speculations, was that what had become of the incarnate in the Blessed Virgin, as narrated by St Matthew and St Luke, was divine Spirit. We have a clear assertion of this in a well-known passage os St Justin (apol 1.33) where the Spirit mentioned in Luke 1.35 is identified with the Logos. A similar teaching was put forward, though more hesitantly, by St Irenaeus (Epideixis 71, 97); and Tertullian (Adv. Prax. 26f) and St Hippolytus (Con. Noet. 4; 16) were also among its exponents. In St Callistus it reappeared couched in a form hostile to the Logos teaching. The fact that so many theologians of different schools reflected this Spirit-Christology encourages the suspicion that it was the most widespread view in the Roman church of the late second. If we are inclined to ascribe R’s (ancient Roman Baptismal Creed) redaction to this period, we should be prepared to look for ideas akin to those described behind the wordings of its second article.