Comment by arkey

> These are people who seem to put in more effort than most, and are sincere in their belief.

No, check this out:

"have WE not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?"

They are not sincere in their belief. Real Christians believe and rely in Christ and His work alone. The people this verse refers to are to the end clinging to their own merit and trying to earn their salvation through their own works rather than rely on Christ's perfect work on the cross.

Saved by Grace alone through Faith alone.