It is not in virtue of its liberty that the human will attains to grace, it is much rather by grace that it attains to liberty.
Saint AugustineEveryone who observes himself doubting observes a truth, and about that which he observes he is certain; therefore he is certain about a truth. Everyone therefore who doubts whether truth exists has in himself a truth on which not to doubt.... Hence one who can doubt at all ought not to doubt the existence of truth.
Saint Augustine