The treatise on grace and law in Summa Theologica begins with the topic of practical philosophy before it talks further about the origin of theology, God. Therefore, Summa Theologica is not only a work of philosophy but also a masterpiece of theology. As for the treatise on law, his primary purpose is to deepen the concrete content of faith. And through discussing the multiple aspects of law, he explores its universal foundation-the eternal law. Aquinas' treatise on law covers the eternal law, the natural law, the human law, the law of the New Testament and the law of the Old Testament. Aquinas stresses over and over again: though law is important, neither can the good be done nor the truth be found, if human nature is not blessed with grace or one doesn't make good use of God's grace. In other words, the state of perfection can't be achieved through simply abiding law.