The four books of the Summa contra Gentiles were written by Thomas Aquinas between 1259-1265, before the considerably larger and more influential, Summa Theologica. The purpose of each work was different. Whereas the Summa Theologica addressed the faithful, especially theology students, the intention of the Summa Contra Gentiles (Systematic Exposition Against Non-Christians) was to speak to a non-aligned and even hostile audience. To that purpose, Aquinas presented arguments ‘refuting specific beliefs or heresies.'

In this famous treatise, St. Augustine (AD 354 - 430) covers the question of the role of free will in our lives and how it contrasts with the role of God's grace. He gives scriptural arguments to show that we cannot earn the grace of God, yet this does not deny the role that free will plays in our own salvation.

The Enchiridion, or as it is sometimes titled, Faith, Hope, and Love, is a short treatise on Christian piety, written in response to a request soon after the death of St. Jerome in 420. The essay was meant to serve as a model for Christian instruction (catechesis).

The work constitutes an exposition of the several clauses of the so-called Apostles’ Creed. The questions concerning the mutual relations of the three Persons in the Godhead are handled with greatest fullness; in connection with which, especially in the use made of the analogies of Being, Knowledge, and Love, and in the cautions thrown in against certain applications of these and other illustrations taken from things of human experience, we come across sentiments which are also repeated in the City of God, the books on the Trinity, and others of his doctrinal writings. The passage ...

Jonathan Edwards was a Protestant theologian and a leading revivalist preacher during the Great Awakening. Edwards wrote Freedom of the Will in the 18th century while working as a missionary to a tribe of Housatonic Native Americans in Massachusetts. He carefully drew out the differences of thought between the Calvinist and Arminian theologies and sided with the Calvinist views on humanity's will. Edwards sought to understand God's foreknowledge and how it related to free will and the ability to choose between good and evil.