What's an "is not"?
Revelation 17:8 The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is.
John was told that the beast "was" (past), "is not" (present), and "shall ascend" (future), so I think that is why most say that this first "is not", in line 8, simply indicates that in John's day that beast was no longer alive. However, later in that same line, it is speaking about people at least 1900+ years after John's day, that they'll wonder when they behold the beast that "was" (past), "is not" (present), and "yet is" (present, also). Does it simply mean that someone who had lived and died before John's day, who stayed dead for a couple millennia, but then was found alive again? Or does, "is not", and "yet is", indicate a dilemma? Will the beast simultaneously "be" and "not be"? It doesn't say when they behold the beast that "was not", but "is not" at the moment they behold him? Will they marvel that he "is not" and "yet is", both at the same time?