Adam Carl August von Eschenmayer is not a well-known figure in the history of philosophy. Even among scholars working on the German Idealist tradition, he tends not to be valued as a major philosopher in his own right; indeed, it would take a serious stretch of the imagination to suggest that Eschenmayer was one of the great post-Kantian thinkers, on a par with J. G. Fichte, F. W. J. Schelling, and G. W. F. Hegel. He was, however, one of Schelling's most perceptive and provocative critics during the first decade of the nineteenth century. From 1797 to (at least) 1812, Eschenmayer and Schelling repeatedly influenced and contested one another's work. Hence, Marquet describes Eschenmayer as a ‘curious interlocutor who reappears at each important turn in [Schelling’s] thought’, and Roux remarks that Eschenmayer was both Schilling's ‘opponent’ and ‘companion of choice’. Even the anglophone literature has come to acknowledge in passing the importance of Eschenmayer's provocations: Vater names him as a key ‘collaborator’ of Schelling’s; Grant devotes several pages to him in Philosophies of Nature after Schelling; Zammito has recently written of his ‘crucial contribution to the emergence of philosophy of nature’; Förster's critique of Schelling in The Twenty-Five Years of Philosophyacknowledges his importance; and Lauer and Wirth chart his role in the genesis of Schelling's account of reason and personality.

It is customary to speak of three major controversies between Eschenmayer and Schelling:

• 1. An exchange in January 1801 to be located in the pages of Schelling's own Journal of Speculative Physics, comprising Eschenmayer's first critical review of Schelling's early philosophy of nature, Spontaneity = World Soul, and Schelling's editorial response, On the True Concept of Philosophy of Nature. Appearing together, these texts contain Eschenmayer's extensive critique of Schelling's early work and Schelling's own defence that ambivalently appropriates many of Eschenmayer's central concepts and concerns, while also announcing the advent of his new form of metaphysics that was to be published in the May 1801 issue of the same journal as the Presentation of my System of Philosophy.

• 2. A fierce debate in 1803–4 over the respective capacities of philosophy and faith to explain the emergence of difference from identity, undertaken not just in their correspondence but also in Eschenmayer's Philosophy in its Transition to Non-Philosophyand Schelling's notorious response, Philosophy and Religion.