Comparative literature on French influence on Goethe is predominantly concerned with Rousseau. In seeking to redress that imbalance, this thesis offers the first comprehensive study of Diderot's and Goethe's art theory. It treats that theory as a whole, and places it in the context of the social and philosophical thought which preceded it. The first part of the thesis studies Diderot's and Goethe's thought on the visual arts and the theatre. That thought reveals different attempts to assert, through the creativity of the artist, man's dominance over nature. This first part also shows that the unrecognised differences between Diderot and Goethe lie less in their discussion of the production of art than they do in their discussion of the beholder. The second part opens with a study of Rousseau. Rousseau's concern to reinstitute in civil society the unmediated exercise of the will assumed from the state of nature grounds a suspicion of the imagination at odds with the art theory discussed in part one. Diderot's unique contribution to the natural law tradition rests, however, on the understanding of the imagination developed within his art theory. For its part, Goethe's art theory of the 1790s provides remarkable affinities between the contemplation of the object of art, and the harmony between the senses and the understanding sought in Kant's and Schiller's aesthetics. Despite such synthesis, the final chapter identifies a normativism in Goethe's later art theory more in keeping with the absolutist tradition before him, but which does not obscure the similarities between his thought and Diderot's. The thesis closes with a brief consideration of the broader relevance of such a comparison.