In its most famous section, its author argued that it is impossible for everything to be contingent, therefore God must exist.
In one section of this work, the author argues that our life can only result in imperfect happiness, and that all our good actions are working toward the ultimate goal of perfect happiness in the afterlife. This work lists sovereign authority, right intention, and righteous cause as the three major components of a just war. In its most famous section, its author argued that it is impossible for everything to be contingent, therefore God must exist. Other arguments include one borrowed from Aristotle, the "Unmoved Mover," as well as the teleological argument. For 10  points, name this work, which lists the quinquae viae as proofs for God, the magnum opus  of St. Thomas Aquinas.
In one section of this work, the author argues that our life can only result in imperfect happiness, and that all our good actions are working toward the ultimate goal of perfect happiness in the afterlife.
Summa Theologica [Accept Summa Theologiae.]