Proving the Existence of God
The central thematic issue confronted by Aquinas in this work is his cosmological argument proposing five ways to demonstrate the existence of God. These five ways are by reference to motion which necessitates the existence of a first mover, by reference to causation, by reference to contingency, by reference to gradations of perfection existing in the world and by reference to design through order and harmony existing throughout the universe.
Truth and Lies
Aquinas addresses what may seem a minor philosophical theme, but which has the potential for unlimited consequence by insisting that humans should live under a permanent assumption that telling the truth is always better than lying. While he admits to gradations of seriousness on the subject of not being truthful and even accepts that in some cases lie can be helpful, he also insists on drawing a difference between harmless lies and malicious lies. Malicious lies attain the level of mortal sin. At the center of this argument is the moral grievance of trying to persuade someone of something that is not true and a small harmless lie is just as untrue as malicious one.
The Essence of Law
Aquinas outlines for conditions of law. It is created for the common good through ordinance of reason. Law should be rationally commanded with the underlying directive to do that which is proper. A sovereign or his representatives should be the entity which issues and maintains the authority of the law. Finally, the law can be considered binding if it is known; ignorance of the law is a burden thus placed on those who administer.
Apprehension without Comprehension
The intellect can only come to know parts of God and those parts will be seen far from their true perfection, but those blessed with divine grace will receive the divine charity of seeing God in a state much closer to His perfection. This is Aquinas’s famous state of achieving beatific vision. Even beatific vision is mere apprehension of God, however, since God is an infinite being. That being so, only another infinite being has the capacity to actually comprehend God, which leaves man to be satisfied with what remains still a great feat for most men: to apprehend the existence of being they cannot comprehend.