Grace and gratitude belong together like heaven and earth. Gratitude evokes grace like the voice and echo. Gratitude follows grace as thunder follows lightning.
Sin is not confined to the evil things we do. It is the evil within us, the evil which we are.
Man can certainly keep on lying (and does so), but he cannot make truth falsehood.
There is no philosophy that is not to some extent also theology.
Radically and basically, all sin is simply ingratitude.
True theology is an actual determination and claiming of man by the acting God.