Michel Serres proposes that we reform our relation to the non-human world by striking a new contract to extend democratic rights and legal protections to nature. Following Serres’s lead, this has for the most part been understood in strictly legal terms. In this paper, I will show that the natural contract also has a narrative dimension, and moreover that taking this into account reveals an engagement with the Principle of Sufficient Reason that puts the relation of the natural contract with law in a new light. The natural contract appears not as a standalone, law-based response to the climate emergency but as part of an ongoing rational practice that involves the law, the sciences, and a wider narrative exploration of the human and the non-human. After outlining Serres’s proposal for a natural contract, I will look briefly to his account of Lucretius in The Birth of Physics where both narrative and contract play an important part. Law is treated as a regularity arising from the connection between events, and further as a form of equilibrium modelled on the most advanced knowledge available. Serres’s discussion of Leibniz’s Principle of Sufficient Reason in The Natural Contract shows that the composition of such an equilibrium is both narrative and rational.