Justin Martyr (103-165 A.D.), also known as Saint Justin, was an early Christian apologist. He wrote apologies and dialogues to defend the Christian Faith from false charges that were brought against Christianity. However, only two apologies and a dialogue survived till this day. Majority of his works are lost in the history.
In his “Logos Christology,” Justin Martyr tries to articulate the relation between the First and the Second Godhead of the Trinity, the Father and the Son, borrowing the language of Logos from the Gospel of John 1. We might say it the Logos Theory. He draws the analogy between the Spoken Word and the Divine Word from John 1, “In the beginning…” The Spoken Word has power and its independent existence and influence. For example, when I speak, words from my mouth go forth which are my own. They bear my authority. Thus, I am not diminished.
In the same way, when God said, “Let there be light,” the Word or Logos comes forth from God. The “said” is the Word that comes to exist. So, this is a sophisticated logic to explain the relationship between the Father and the Son in the biblical Christianity. However, it has flaws in its analogue, as the Word comes forth from the Father. This shows that Jesus/Son or the Logos began to exist at some point of finite time. In other words, Jesus is not fully divine or lesser divine than the Father, hence the Son is not fully equal member of the Trinity. Therefore, Logos Christology does not reflect the true doctrine of the Trinity, but it has very similar characteristics of Sabellianism or Modalistic Monarchianism.