This paper examines Jean le Rond d’Alembert’s views of metaphysical cosmology and argues that these constitute an important context for Kant’s critical-period response to rational cosmology. D’Alembert is commonly taken to have dismissed cosmology from the roster of the legitimate sciences, and there is indeed evidence of his scepticism towards Maupertuis’ cosmology no less than towards Wolff’s cosmologia generalis . I argue, however, that a broadly Leibnizian cosmological perspective underpins d’Alembert’s accounts of our knowledge and of the task of the philosopher. D’Alembert’s work thus anticipates and helps bring into focus Kant’s own nuanced engagement with the cosmological tradition.