yes the demon that is IN them that fall away is singular- " a devil" but that devil is IN THEM that perish- that fall away into perdition this is the mystery of iniquity.
2Th 2:9 [Even him], whose coming is after the working of Satan with all power and signs and lying wonders,
2Th 2:10 And with all deceivableness of unrighteousness
in them that perish; because
they received not the love of the truth, that they might be saved.
2Th 2:11 And for this cause God
shall send them strong delusion, that they should believe a lie:
2Th 2:12 That
they all might be damned who believed not the truth, but had pleasure in unrighteousness.
singular spirit- antichrist- error- perdition who is in THEM that fall away- THEM that perish.
there was ONE judas who betrayed Jesus who the devil was in- there will be more than one judas to come who the same devil is in.
They mystery of godliness is this:
Col 1:27 To whom God would make known what [is] the riches of the glory of this
mystery among the Gentiles; which is
Christ in you, the hope of glory:
But while these in 2 thess 2 are suppose to be of the above verse, they fall away because the truth of them is this:
2Th 2:7 For the mystery of iniquity doth already work: only he who now letteth [will let], until he be taken out of the way.
2Th 2:8 And
then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
2Th 2:10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
this wickedness is IN THEM and it shall be revealed- what will reveal it?
2Th 2:3 Let no man deceive you by any means: for [that day shall not come], except there come a falling away first, and that man of sin be revealed, the son of perdition;
It is revealed when they FALL AWAY.- Jhn said the same thing
1Jo 2:18 ¶ Little children, it is the last time: and as ye have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last time.
1Jo 2:19 They went out from us, but they were not of us; for if they had been of us, they would [no doubt] have continued with us: but [they went out], that they might be made manifest that they were not all of us.
LOOK these antichrists WENT OUT FROM US because they were not really of us and they went out SO IT WOULD BE MANIFEST(revealed) that they are not of us!
wow God is awesome