The chapter examines how Kant casts his critical philosophy in the Prolegomena, and in particular how the accusations of being a Berkeleyian force him to refine his views about what exactly the mind-dependence of appearances involves. After looking at what exactly Kant means by ‘a priori intuition,’ the essay explores three main ways to make sense of his transcendental idealism – roughly, an epistemic account, a phenomenalist or ‘mentalist’ view and a relationalist interpretation – and argues that the last of these provides the most fruitful approach to the arguments in the Prolegomena, including the examples involving incongruent counterparts. On this view, the Prolegomena stands as an important stage in Kant’s development precisely in its repudiation of Berkeleyian phenomenalism, and while it is only in the B-edition of the first Critique that transcendental idealism is fully presented, the Prolegomena marks a clear advance over the A-edition.

This chapter analyses the careers of two distinct narratives about Mach’s philosophical legacy that prevailed among German-speaking physicists and philosophers for more than a generation. Planck’s polemic against Mach sired the idea of a Machian philosophical system that was irreconcilable with modern physics, Boltzmann’s legacy foremost. But Planck also bereaved Mach’s positivism of its naturalist foundation and identified it straight with phenomenalism. In contrast, many Austrians considered the epistemologies of Mach and Boltzmann as even mutually supportive for a defence of empiricist indeterminism. Taking positivism in its original, more general understanding, they underscored Mach’s broader anti-metaphysical and empiricist stance, eventually adopting him as a standard-bearer for the new movement of Logical Empiricism. While these understandings were not necessarily tied to a positive or negative assessment, they often amounted to simplifications, transformations, or even contortions of Mach’s thinking, which made it increasingly difficult to declare oneself in Mach’s footsteps and simultaneously to advocate scientific modernism.

The aim of this chapter is to provide a thorough account of the fact that Ernst Mach and Friedrich Nietzsche are often associated with each other in the specialised literature on the history of philosophy and the philosophy of science. I argue that the consistency which can be discovered between them is much more substantial than one may imagine. On the basis of their conception of knowledge and truth, it is possible to outline a complete parallelism between their approach to the issue concerning our intellectual relationship with the external world. In fact, Mach and Nietzsche dealt with the very same questions and indeed pursued a common general aim, namely the elimination of worn-out conceptions from the world of modern culture. Furthermore, I will maintain that Mach’s and Nietzsche’s research interests converge on the classic problem of realism versus anti-realism, and that it is in the light of this particular issue that their own views can be compared.

Ernst Mach’s works have often been interpreted as presenting some version of idealism, such as phenomenalism. However, Erik C. Banks’ recent case for the rival neutral monist reading seems persuasive. But it still leaves a problem: how to explain why so many intelligent and thoughtful readers, some of them sympathetic to Mach, thought of him instead as some kind of idealist. I set out the major factors which tempt people into reading Mach thus and assess the strengths and weaknesses of these two readings.