Saint Augustine of Hippo was one of the most profound and prolific of the Church Fathers, and he expresses a variety of different views of free will and truth over his long careers. As his Retractions demonstrate, his views did not remain consistent over his long career but developed as he continued to pray, reflect, read, and gain experience.
On God as Truth, the earliest discussion is in de Magistro, in which Augustine argues that because of the incommensurability of things and words, only the divine logos, being word made flesh, can be a precondition of true statements, because in the Logos word and thing are blended. Without God, there can be no truth.
Augustine is one of many writers who struggles with the problem of the relationship of free will and predestination. For him, neither sin nor salvation would be possible without free will because both depend on the ability of humans to make moral choices.