For many are called, but few [are] chosen. Matt 22:14 "Chosen" = eklektos (G1586), from whence the word "elect" comes from. These shall make war with the Lamb, and the Lamb shall overcome them: for he is Lord of lords, and King of kings: and they that are with him [are] called, and chosen, and faithful. Rev 17:14 Being "elected" by God is not enough to be a member of Christendom. Rather, you must also be faithful. So, to prove that Election is unshakeable, you must show that being "elected" (chosen) automatically inspires unshakeable faith — to wit, a faith that cannot backslide. But, Hebrews 6:4-8 clearly speaks of those who Believed, but then backslid. And, this seems to be the warning of Matt 24:24 as well, "For false Messiahs and false prophets will arise and will show great signs and wonders, so as to mislead, if possible, even the elect." So, it seems to me that all are called (John 12:32; cf. Luke 12:32)... some are chosen / elected... and of those, only the Faithful are members of the Body of Christ — whereas, indeed, Hebrews 6:4-8 warns that those who backslide after Believing are doomed.