Although the influence of such philosophers as Holbach, Condorcet, and Godwin on Shelley's theory of the perfectibility of man has been noted, that of Pierre Jean George Cabanis, the French materialistic physician of the eighteenth century, has been overlooked. Yet Cabanis's ideas as put forward in his most considerable work, Rapports du Physique et du Moral de l'Homme, cited in the notes to “Queen Mab,” on the important relation between man's physical well-being and his intellectual and moral health appear to have contributed a striking feature to the poet's exposition of his views in “Queen Mab” and even in “Prometheus Unbound.” If it be remembered that Shelley already, by virtue of his vegetarianism, considered that man cannot become morally perfect unless he be physically perfect, it is not surprising that Cabanis's emphasis on the same idea from another angle, namely, the necessity of a mild and equable climate for the best development of intellect and morality, impressed the poet to such an extent that he incorporated the physician's belief in his theory of perfectibility. His ready acceptance of Cabanis's ideas is the less surprising when it is remarked that Cabanis was also a perfectibilian, believing that man “est indéfinement perfectible, et qu'il devient en quelque sort, capable de tout.”