2 Thess. 2:8-12 is the key.
8And 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:
9Even him, whose coming is after the working of Satan with all power and signs and lying wonders,
10And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11And for this cause God shall send them strong delusion, that they should believe a lie:
12That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
According to the Bible itself, those who have heard the gospel and rejected it, "That they all might be damned who believed not the truth, but had pleasure in unrighteousness."