Justin thus believed in a co-equality and unity of the Son and Father, of both being of the same substance and undivided, but did not teach the co-eternity of the Son which was enshrined in the Nicene doctrine; for Justin, there was a point in time before creation when the Son was begotten.
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Were Early Christians Trinitarians? Robert Hommel
Like most of the Fathers, Justin's Christology (his concept of Christ's nature) is not fully spelled out in his writings. It is true that he refers to Christ as a "second God" in his dialog with Trypho. He refers to the origin of the the Pre-Incarnate Christ (the Logos) as "begotten before all creation." Some scholars have concluded that therefore, Justin did not conceive of the Logos as being eternal (8a).
It would be a mistake, however, to read later Arian thought back into Justin's words. Justin's term "second God" occurs in his dialog with Trypho, a Jew. Justin is trying to demonstrate to a devout monotheist that there is another Person in the Bible who is called "God" (8b). He does so by citing various theophanies in the OT (Dialog with Trypho, ch 56), by citing passages in which two "Gods" appear in the OT (IBID, ch 58, 60, 126), as well as evidence from the NT, such as Heb 1:8 in which the Father calls the Son "God" (IBID, ch 56). It must be noted that in each of these references, the implicit meaning is that the Logos is truly God - distinct from the Father and subordinate to Him, yet essentially one with Him as well. This meaning becomes explicit when Justin discusses passages in which LORD (YHWH) is ascribed to "two Gods:" "It must be admitted absolutely that some other one is called Lord by the Holy Spirit besides Him who is considered Maker of all things" (IBID).
Regarding the origin of the Logos, Justin provides two brief explanations (like the other Fathers, Justin is not writing a systematic theology):
The first explanation centers on the word "begotten" or its synonyms. Justin says the Logos is "begotten before all creation" (Dialog with Trypho, ch 129), the "First-Begotten of God" (First Apology, ch. 58), and "Firstborn of God" (First Apology, ch 46). He contrast the Logos as Begotten with the Father, who is Unbegotten. Nevertheless, he did not teach that the Logos was "created," as the WT states. While he doesn't specifically contrast the two terms, Justin avoids using the term "created" in reference to the Logos (though he does quote Trypho using poiew of Him [Dialog with Trypho, ch 64]), and he clearly has this contrast in mind when he employs the second of his explanations of the origin of the Logos.
The second explanation is to use the analogy of light from the sun (Dialog with Trypho, ch 128). He thereby expresses his conviction that the Son is of one substance with the Father - light from light - and yet distinct from Him. Thus, like most of the Early Fathers, Justin believed the the Father is the source of divinity, for when the sun sets, the light is gone. The Son has no independent existence apart from the Father, and so while Justin says there are Two Gods, he also says there is one Source, and thus he is not a ditheist. Justin is careful to point out that while this analogy is useful, it is not a complete picture. By "begetting" the Light of the Logos, the Light of the Father is in no way diminished. He therefore attempts a second analogy, that of fire (IBID). For while one fire can kindle another, it is not itself diminished by the kindling. There can be no diminishing or cutting off of God - He is eternally unchanged by the begetting of the Son. Finally, Justin offers the analogy of the spoken word, which does not diminish the speaker when is is spoken, but yet which is comprised of the very Reason of the one who Speaks.
Justin never precisely defines when the begetting of the Son takes place, and this ambiguity has led some to speculate that Justin could be viewed as a proto-Arian. However, since Justin does not address this issue directly, it is impossible to be dogmatic on this point. Justin speaks of the Son being "begotten" before all creation, and thus all we can say with any certainty is that for Justin, whenever creation took place, the Logos already existed. Further, as we have seen, Justin did not believe that Logos was a created being, and indeed called him a "second God" (not an Arian "secondary god") alongside the Father (there were, of course, no capital letters in the original Greek, but context makes the distinction clear).
Thus, for Justin, the Son is "begotten, not made" of the same substance as the Father. The begetting of the Son precedes creation, and may precede time as well. The Father is the source of the Godhead (or Divinity). In his Christology, then, Justin precedes Origen and much later Trinitarian formulations (e.g., the so-called "Cappodocean solution"; Eastern Orthodoxy still teaches that the Father is the source of divinity).