Left Behind

40 Then two men will be in the field; one will be taken and one left. 41 Two women will be grinding at the mill; one will be taken and one left (Mt 24:40-41).

This is a stock prooftext for the pretribulational rapture. There are, however, problems with that inference:

i) In the pretrib scheme, as I understand it, Jesus first comes for his people (the rapture), followed by the great tribulation (7 years), followed by the Second Coming proper. But the text in Mt 24 doesn't separate a rapture from the Parousia, with the great tribulation in-between. So a pretriber must interject that distinction into the text. 

That doesn't disprove his position. He can claim that his position is a synthesis of many different passages. But that means he's plugging Mt 24:40-41 into a larger frame of reference. He can't derive a pretribulational scheme directly from vv40-41. But in that case it can't be a prooftext for the pretrib position. Rather, it takes that reference frame for granted. So the appeal is circular. 

ii) That still leaves the question of what event vv40-41 represent. Hard to say for sure since the imagery is rather vague. Based on the comparison with Noah's flood (vv37-39) as well as angels rounding up the elect (v31), the imagery might suggest God evacuating the elect from the danger zone. Those "left behind" face the judgment. The elect are physically separated from the wicked. Sequestered for their own protection. For instance, Noah's family was taken into the ark to protect them while the wicked were left outside to drown.

iii) Then there's the question of how literally to take the implicit imagery. Does all this happen on earth? Are the elect evacuated to a refuge somewhere on earth while the damned are exposed to judgment elsewhere on earth? Are the elect transported to a parallel universe containing an Edenic earth while the original earth becomes a global hellhole?