This study considers how ancient sources, from New Testament texts until Augustine’s initial anti-Pelagian writings, understand the relationship between nature and grace. This background is essential for understanding the nature/grace distinction as it is employed at the end of the fourth century AD and as it influences the thought of Augustine and his rivals. I argue that in ancient treatments of nature and grace, both Christian and non-Christian, we find two related but distinct conceptual models. The first may be called a property model: nature and grace are coupled in describing what things are, their essence, as distinct from the properties they can receive, including potential gifts or benefits. The second model may be called biological or filial: nature and grace are coupled in distinguishing inborn status from adoptive incorporation into a new set of relations.