On Nature and Grace (Latin: De natura et gratia) is an anti-Pelagian book by Augustine of Hippo written in AD 415. It is a response to Pelagius's 414 book On Nature (Latin: De natura). Before this work, Augustine did not seem to see Pelagius as a heretic, but On Nature and Grace seems to be a turning point in the Pelagian controversy.[1] The work does not mention Pelagius by name, but by responding to De natura, Augustine for the first time engages Pelagius as an opponent.[2]