I will begin to test the beliefs of Jehovah’s Witnesses with my favorite scripture John 20:28. Lately, I have used this verse in every one time encounter at my door or on the street. It has been very effective and no one has adequately answered it.
John 20:28 “Thomas answered and said to Him, ‘My Lord and my God!’”
Jesus had risen from the dead and appeared to the disciples. However, Thomas was not present at that meeting. As the disciples explained how Jesus appeared to them, Thomas said unless Jesus showed him the nail prints in His hands and feet and the hole in his side he would not believe. Jesus then appears to Thomas and tells him to touch his wounds and believe. We read verse 28: “Thomas answered and said to Him, ‘My Lord and my God!’” Thomas clearly called Jesus the one true God. This passage seems to contradict the doctrine of the Jehovah’s Witnesses that Jesus is a lesser god; a created being.
One explanation they have given me was Thomas was using God’s name in vain. Similar to when we get frustrated and say, “My God what’s wrong with you?”
This is an extremely poor answer. Nowhere in early religious writings or in the New Testament do we see a Jewish person or anyone making statements even close to “Oh my God.” It was not part of the language during the time of Jesus or the early church. This is a very recent expression. Plus a very religious monotheistic Jew would never say something like that. Using God’s name in vain would be breaking the 3rd commandment. They revered the name of God. In fact even today they do not even write the name of God. What you see in much of the Jewish literature is G-d. At the web site Judaism 101 the author writes this about God as the creator: “In general, Judaism views the existence of G-d as a necessary prerequisite for the existence of the universe.” If Thomas was using God’s name in vain and thus breaking the 3rd commandment, we would expect to see Jesus correct him. Instead in John 20:29, “Jesus said to him, ‘Because you have seen Me, have you believed? Blessed are they who did not see, and yet believed.’” Jesus commends Thomas and anyone in the future who believe He is Lord and God.
A second explanation I have heard was that Thomas said to Jesus “My Lord” and then looked to heaven and said “My God.” Witnesses say Thomas never called Jesus God, he was acknowledging Jehovah in heaven.
First, nowhere does the text say Thomas looked to heaven and prayed to the Father. The Jehovah’s Witnesses simply assume their viewpoint is true and then trying to make sense of the verse. This is a logical fallacy called circular reasoning. The text doesn’t teach Jesus is a lesser god; they assume it. Second, it says Thomas said to “him,” singular. He was only addressing Jesus. Therefore, the words “my Lord and my God” apply to Him alone. Third, if Jesus was not God, Jesus should have rebuked Thomas for blasphemy. Instead we see him commending him for what he said. Fourth, the Greek text actually says, “The Lord of me and the God of me.” In calling Jesus God, Thomas used the Greek words “ho theos” = the God. A Jehovah Witness cannot add the article “a” here because in the Greek there already is the article “the.” Therefore, Jesus cannot be a god, a mighty god, or a lesser god but is in fact almighty God. Utilizing “ho theos” John is emphatically saying Jesus is “the God.”
I have never heard a good explanation for this text. Most Jehovah’s Witnesses will not try to answer this verse but try to steer you to another set of verses. In Biblical interpretation you should always interpret the unclear in light of the clear. This verse clearly teaches Jesus is God. Once this is understood then you can properly interpret those verses that could be deemed controversial.
The Jehovah’s Witnesses you share this with will walk away with a large stone in their shoe. In one verse you have given them something to think about.
One morning I was jogging down a street and I saw two Jehovah’s Witnesses talking with a man; I knew I needed to get involved. When I shared John 20:28 with one of them, he was stunned. He couldn’t believe that Thomas called Jesus “the God.” He said he would go home to check to see if the Greek actually said “ho theos.” I don’t know if he ever followed up on what he said he’d do but if he did he would discover what I told him was true. It could be he is no longer a Jehovah's Witness. This is why we share the truth in love. You never know what God will do with a simple truth.
 “The Kingdom Interlinear Translation of the Greek Scriptures,” Watchtower Bible and Tract Society 1985