It is possible to demonstrate God's existence, although not a priori, yet a posteriori from some work of His more surely known to us.
Thomas AquinasA man should remind himself that an object of faith is not scientifically demonstrable, lest presuming to demonstrate what is of faith, he should produce inconclusive reasons and offer occasion for unbelievers to scoff at a faith based on such ground.
Thomas AquinasNothing created has ever been able to fill the heart of man. God alone can fill it infinitely.
Thomas AquinasGood and evil are essential differences of the act of the will. For good and evil pertain essentially to the will; just as truth and falsehood pertain to the reason, the act of which is distinguished essentially by the difference of truth and falsehood (according as we say that an opinion is true or false.) Consequently, good and evil volition are acts differing in species.
Thomas Aquinas