Jesus Himself told the disciples that His return would be so prominent and observable that everyone would immediately know it was happening. Thus, He reveals in Matthew Chapter 24 that if someone comes forward and reports that He has already returned, it will not be true:
“‘Then if anyone says to you, “Behold, here is the Christ,” or “There He is,” do not believe him. For false Christs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect. Behold, I told you in advance. If therefore they say to you, “Behold, He is in the wilderness,” do not go forth, or, “Behold, He is in the inner rooms,” do not believe them. For just as the lightning comes from the east, and flashes even to the west, so shall the coming of the Son of Man be.’” Matthew 24:23-27 (emphasis in original).
So could the Watchtower still be correct that Jesus already returned invisibly in heaven in 1874 (or 1914)? Or does the Bible indicate differently?
The Bible vs. The Watchtower 