A glimpse into eternity, either a view of Heaven or Hell would do nothing to convince the unregenerate. They will still, continually without ceasing, suppress the truth down in unrighteousness as that is the only thing they know.

5 And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.

Romans 1:18
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;