Pope John Paul II taught a series of catecheses on the mystery of the indwelling of the Holy Spirit in the sacramental life of the faithful Christian. The anthropological aspects of the agency of the human heart—its capacity for the gift of love and to give love in return—lived out in moral acts of social justice has since become known as his Theology of the Body. Seen more specifically as a development in perennial wisdom of Church dogma, the Natural Law, the indwelling of God in the human heart is, as taught by St. Augustine a gift of grace, perfecting nature. This philosophical approach to a deeper theological truth of the human person's need for God was developed into a systematic metaphysics by St. Thomas Aquinas, Man as the image of God.