Question:How would you build up an apologetic defense against a Unitarian argument about John 20:17? In John 20:17 Jesus is speaking to Mary Magdalene: Jesus said to her, “Stop clinging to Me, for I have not yet ascended to the Father; but go to My brethren, and say to them, ‘I ascend to My Father and your Father, and My God and your God.’ ” There are Unitarians who say because Jesus said "My God" (which He also said on the cross) that He can't be God so they deny the Deity of Christ.
Answer:The basic argument of all Unitarians that I have seen so far come down to this. They take one passage at a time and ask: "Is this logical?" (to interpret it to imply Jesus is God). But we have never claimed that the deity of Jesus is logical. "In the beginning was the Word and the Word was with God and the Word was God." (John 1:1). Where is the logic here? The question is not whether the biblical picture of Jesus is logical by human standards. The question we must ask is, "What does the Bible say?"
Here is the bottom line. The Bible says that "The Word was God." It also says dozens of things which make it absolutely plain that Jesus is God. I will not list all of them here, but there are dozens of passages in the New Testament (and several in the Old as well, by the way: Isaiah 7:14, Isaiah 9:1,6-7, Zechariah 11:13). The deity of Christ is a mystery--it is not "logical"--but it is nevertheless true. [note: http://evidenceforchristianity.org/how-do-i-convince-a-jehovah-witness-that-jesus-is-god/ and http://evidenceforchristianity.org/jehovahs-witness-notes/]
Obviously, if we take John 20:17 alone, out of its context, it could be taken two ways. So the Unitarian does not ask, "What is the most obvious interpretation, in the context of all Scripture?" No. What they as is "which is the most logical interpretation of this one passage?" Sorry, but this is the wrong question to ask. The cross of Christ is not logical. The incarnation is not logical. But they are nevertheless true. Paul told us that "Greeks look for wisdom."(1 Corinthians 1:22). The schoars and philosophers and Unitarians of this age look for what appeals to their reason. They therefore stumble over the Jesus of the Bible.
The fact that Jesus talked about the Father and about his God/Father in John 20:17 does not disprove the deity of Christ. The only way it could disprove it is if we take as a presupposition that the Son/God cannot call the Father God. But this is a presupposition, making the argument circular. One cannot use circular reasoning to prove what this passage means, but that is what the Unitarian does. We should not fall into this trap.
"In Christ the fullness of deity dwells in bodily form." (Colossians 2:9). "The Word/God became flesh and made his dwelling among us. We beheld his glory--the glory of the one and only Son of God." (John 1:16). "You, a mere man, claim to be God." (John 10:33). God the Son--Jesus Christ--called his Father "God". That is true, but it does not prove that he is not God. How should we interpret John 20:17? Let us interpret it in the light of clear passages such as the Old Testament and New Testament passages I have cited.
What the Unitarian wants to do is argue with you, based on logic, one scripture at a time and use this logic and bogus hermeneutics to logically prove Jesus is not God. I would plead with anyone that they please not fall prey to this heretical teaching.
An aside: Just this past weekend I had a sad and difficult interaction with a believer who appears to have fallen for the Unitarian heresy. Let me give an example of the kind of bad hermeneutics such Unitarians use, as he attempted to use on me this weekend. He wanted to refute the rather obvious interpretation of John 8:58--"Before Abraham was born, I AM." Here, Jesus is obviously claiming, not only to have pre-existed Abraham but to have pre-existed creation itself. He does not say "before Abraham was born, I was." No, he says "before Abraham was born, I AM." My friend's argument was this: "Jesus is not using the tetragramaton (YHWH) here, so he is not taking the name of God." Let me respond to this claim. In John 8:58 we have a Greek translation of what Jesus said. How does my friend know that Jesus did not use the tetragramaton? The tetragramaton is Hebrew, not Greek! Here is a question: If John were to translate the tetragramaton into Greek, what would be the closest possible translation? In John 8:58, the Greek has (paraphrasing), before Abraham was born, I, I AM. This is as close a translation of the tetragramaton into Greek as could be. So much for my friend's argument. To be honest, I really do not know what Jesus said in Aramaic in John 8:58. For all I know, Jesus did not use the tetragramaton, although this would be the closest equivalent to the Greek used by John. What I do know is that, no matter what Jesus said, he was claiming to be God. That is why many in the crowd picked up stones to stone him.
This is an example of the typically rather weak hermeneutics used by Unitarians to try to disprove the deity of Jesus.
I hope this helps.