Gary
I can appreciate your satisfaction in your trinitarian belief.
Most trintiarian Xians I have met at my hubby's church and within my 'worldly associations' are less seated in trinity's absoluteness mostly because they really don't understand their beliefs beyond that is what they were told in their church.... this is especially true when I make it clear I am not trying to convert them to the WTS.
As for John 20:28..... it can be spun as the WTS does as an expression of shock or even revert back to Isa 9:6 'mighty god' but as Arians point out not 'almighty god.
Deity/divine.....that discussion becomes about co-equal versus inferior between arians and trinitarians
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for the point of conversation with your wife, here is the JW Reasoning Book response to John 20:28
*** rs p. 213 Jesus Christ ***
Does Thomas’ exclamation at John 20:28 prove that Jesus is truly God?
John 20:28 (RS) reads: “Thomas answered him, ‘My Lord and my God!’”
There is no objection to referring to Jesus as “God,” if this is what Thomas had in mind. Such would be in harmony with Jesus’ own quotation from the Psalms in which powerful men, judges, were addressed as “gods.” (John 10:34, 35, RS; Ps. 82:1-6) Of course, Christ occupies a position far higher than such men. Because of the uniqueness of his position in relation to Jehovah, at John 1:18 (NW) Jesus is referred to as “the only-begotten god.” (See also Ro, By.) Isaiah 9:6 (RS) also prophetically describes Jesus as “Mighty God,” but not as the Almighty God. All of this is in harmony with Jesus’ being described as “a god,” or “divine,” at John 1:1 (NW, AT).
The context helps us to draw the right conclusion from this. Shortly before Jesus’ death, Thomas had heard Jesus’ prayer in which he addressed his Father as “the only true God.” (John 17:3, RS) After Jesus’ resurrection Jesus had sent a message to his apostles, including Thomas, in which he had said: “I am ascending . . . to my God and your God.” (John 20:17, RS) After recording what Thomas said when he actually saw and touched the resurrected Christ, the apostle John stated: “These are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in his name.” (John 20:31, RS) So, if anyone has concluded from Thomas’ exclamation that Jesus is himself “the only true God” or that Jesus is a Trinitarian “God the Son,” he needs to look again at what Jesus himself said (vs. 17) and at the conclusion that is clearly stated by the apostle John (vs. 31).
Here is one arian presentation on jesus being divine too via Robert Wagoner (damn I feel like 'Alice-Rachel now)
Is Jesus "Divine"?-- Arian response
Yes, on the strength of Col 2:9 and Heb 1:3. However, there is no specific scripture which uses the word "divine" (Greek theios) for Jesus. The word appears three times; Acts 17:29, 2 Pet 1:3,4. The first two refer to Go d, the third says the church becomes "partakers of the divine nature." In the latter sense, however defined, Jesus would have to be included.
http://www.auburn.edu/~allenkc/grdebate.html