I do not understand this as an address to Jesus; but thus, ”Yes; he it is indeed! He, my Lord and my God!” Yet, in giving this interpretation, I do not affirm that Thomas passed all at once from the extreme of doubt to the highest degree of faith, and acknowledged Christ to be the true God. This appears to me too much for the then existing knowledge of the disciples; and we have no intimation, that they recognized the divine nature of Christ….

I am therefore inclined to understand this expression, which broke out from Thomas in the height of his astonishment, in a figurative sense, denoting only, “Whom I shall ever reverence in the highest degree.” If he only recollected what he had heard from the mouth of Jesus 10 days before (14.9-10), that recollection might have given occasion to an expression which probably Thomas himself could not have perfectly explained; as is often the case with such words as escape us when we are under the most overpowering surprise. 

But yet the expression might be equivalent to saying, “He! my Lord! With whom God is most intimately united, and is in him! In whom I behold God, as it were, present before me!” Or, a person raised from the dead might be regarded as a divinity; for the word God is not always used in the strict doctrinal sense….Besides, the first compellation, my Lord! certainly is directed to Christ.

287. D. Michaelis: Anmerk. in loc.; apud Dr. J. P. Smith’s Script. Test. vol. ii.p. 287. [See another quotation from the same writer (Resurrection of Jesus, p. 272-3), given in “lllust. of Unitarianism,” p. 266, No. 5, second edit.]