The contention that there was a time when the Son as such was not has caused Bernard Lonergan to question the logical coherence of Tertullian’s Christology. Although Lonergan avoids reproaching the pre-Nicenes for their ostensible need to excise incongruous logical elements from distinct theological notions which they espoused regarding the Father, Son and Holy Spirit, he points out that Tertullian’s argument concerning a time when the Son was not in existence conflicts with his fundamental theological case made against Praxeas respecting the three persons. Tertullian supposedly holds that the Son is God as the Father is God. But this does not mean that he believes the Father and Son have every divine-constituting property in common. The Latin apologist is convinced that the Son, being derivative of the divine substance is God (Adversus Praxean 9). Nevertheless, Tertullian also believes that the entity who generates the preexistent Christ is eternal or everlasting, whereas the Son qua Son is not. But Lonergan insists that this position is logically untenable. For if God is everlasting and the Son is God, then the Son must also be everlasting; furthermore, if God is the whole divine substance and Christ is God, then Christ too is identical with the whole divine substance. A claim to the contrary simply appears incoherent, based on the law of transitivity. The logical law of transitivity states that if A=B and B=C, then A=C. Stated non-formally, if Marcus is Tullius and Tullius is Cicero, then Marcus is Cicero. If the term “God” identifies a referent as opposed to predicating divinity of a subject, then Lonergan’s argument seems convincing. However, it is possible that “God” is not a term marking absolute identity, but one that predicates relative identity. And relative identity is most closely associated with terms that philosophers consider “sortal.”
The chief objection to Lonergan’s syllogisms is probably the theory of sortal-relative identity, which certain thinkers view as suspect. The theory of sortal-relative identity claims that it is logically possible for two entities (A and B) to be the same F without being the same G. For example, a couch and chair may have the same color (F) but still be different pieces of furniture (G). Advocates of sortal-relativity thus contend that identity is never absolute. A piece of clay (F) is not the same G as a statue of which it is the material cause. Two entities (A and B) are always discernible in some crucial aspect or relativized with respect to a sortal noun (e.g. bird, dog, cat, chair, star, couch or tree). John Feinberg, Christopher Hughes, Saul Kripke, Peter Geach, Thomas V. Morris and Peter van Inwagen adequately treat the topic of sortal-relative over against absolute identity in their respective studies. While a deeper exploration of identity (relative, absolute, qualitative or numerical) is outside the bounds of this work, this investigation espouses the position that Lonergan’s syllogisms fittingly comport with the theory of absolute identity.
 Bernard J. F. Lonergan, The Way to Nicea: The Dialectical Development of Trinitarian Theology: a Translation [from the Latin] by Conn O'Donovan from the First Part of De Deo Trino (London: Darton, Longman, and Todd, 1976), 48.
 What are here called “divine-constituting properties” are similar to what others call great-making properties. Thomas V. Morris defines a “great-making property as “any property, or attribute, or characteristic, or quality which it is intrinsically good to have, any property which endows its bearer with some measure of value, or greatness, or metaphysical stature, regardless of external circumstances,” in Our Idea of God: An Introduction to Philosophical Theology (Vancouver: Regent College Publishing, 1991), 35. The difference between a divine-constituting property and a great-making property is that while non-divine beings can possess the latter, only a being that is fully divine can possess the former. See Hoffman and Rosenkrantz, Divine Attributes, 13-20.
 Seeberg, History of Doctrines, 1:126.
 See Bertrand Russell, Introduction to Mathematical Philosophy (London: G. Allen and Unwin, 1970), 33; Simon Blackburn, Think: A Compelling Introduction to Philosophy (Oxford and New York: Oxford University Press, 1999), 134.
 See Richard Cartwright, Philosophical Essays (Cambridge, MA: MIT Press, 1987); Hughes, Complex Theory of a Simple God, 157.
 Ibid. 158.
 Ibid. 156-161; Kripke, Naming and Necessity, 3; Peter Geach, “Ontological Relativity and Relative Identity,” in Logic and Ontology, ed. Milton Karl Munitz (New York: New York University Press, 1973); Peter van Inwagen, Ontology, Identity, and Modality: Essays in Metaphysics (Cambridge University Press, 2001); Thomas V. Morris, The Logic of God Incarnate (Ithaca: Cornell University Press, 1986); John Feinberg, No One Like Him: The Doctrine of God (Wheaton: Crossway, 2006), 494-496.