Westminster Confession of Faith:
III. This infallible assurance doth not so belong to the essence of faith but that a true believer may wait long and conflict with many difficulties before he be partaker of it: yet, being enabled by the Spirit to know the things which are freely given him of God, he may, without extraordinary revelation, in the right use of ordinary means, attain thereunto. And therefore it is the duty of everyone to give all diligence to make his calling and election sure; that thereby his heart may be enlarged in peace and joy in the Holy Ghost, in love and thankfulness to God, and in strength and cheerfulness in the duties of obedience, the proper fruits of this assurance: so far is it from inclining men to looseness.
Belloq: You and I are very much alike. Archeology is our religion, yet we have both fallen from the pure faith. Our methods have not differed as much as you pretend. I am but a shadowy reflection of you. It would take only a nudge to make you like me. To push you out of the light.
Indiana: Now you're getting nasty.
Indiana Jones is a true gritty American, who carries the red, white and blue at the beginning of the regiment. Belloq appears pure evil, a Nazi, in with the great forces of evil. But both are fallen; their faith is humanistic and they both believe that knowledge will make them victorious in a fallen world.