Good 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.

In order for a war to be just, three things are necessary. First, the authority of the sovereign... Secondly, a just cause... Thirdly... a rightful intention.

A man does not always choose what his guardian angel intends.

It seems that God does not exist; because if one of two contraries be infinite, the other would be altogether destroyed. But the word "God" means that He is infinite goodness. If, therefore, God existed, there would be no evil discoverable; but there is evil in the world. Therefore God does not exist.

It is not possible to be ignorant of the end of things if we know their beginning.

To pretend angels do not exist because they are invisible is to believe we never sleep because we don't see ourselves sleeping.

Three things are necessary for the salvation of man: to know what he ought to believe; to know what he ought to desire; and to know what he ought to do.