The Summa Contra Gentiles is the second of Thomas Aquinas's three great theological syntheses, written after his Commentary on the Sentences of Peter Lombard and before his Summa Theologiae. The Summa Contra Gentiles is commonly thought to be composed with a missionary intention, possibly for the use of Thomas's brethren in their work of explaining the faith to non-Christians, especially Muslims in Spain. This volume contains the third and fourth books of the Summa Contra Gentiles. Book 3 treats of God's providence over all of creation from the perspective of what can be known on the basis of human reason. Book 4 treats of matters of faith surpassing human reason: the Trinity of Persons in God, the Incarnation of the Divine Word, the Work of Salvation, and the Last Things.