Here, Augustine isn’t primarily concerned about Manichees or other non-Christian critics, but fellow Catholics who disagree with his views of Genesis 1. He doesn’t identify precisely who those critics are or what their objections were, but he begins by establishing those points with which his critics definitely agreed with him—such as that God cannot change, and that while God’s dwelling-place, the Heaven of heavens, can change, it is so constantly and uninterruptedly sustained by God’s light that it does not change (so, it is subject to change like other creatures, but unlike them, it never changes).