This book offers a comprehensive critique of the Kantian principle that ‘objects conform to our cognition’ from the perspective of a Copernican world–view which stands diametrically opposed to Kant’s because founded on the principle that our cognition conforms to objects. Concerning both Kant’s ontological denial in respect of space and time and his equivalence thesis in respect of ‘experience’ and ‘objectivity’, Ryall argues that Kant’s transcendental idealism signally fails to account for the one thing that is essential for Copernicus and the only thing that would validate a comparison between his and Kant’s critical philosophy, namely the subject as ‘revolving object’. It is only by presupposing – in a transcendentally realistic sense – that human beings exist as physical things in themselves, therefore, that the ‘observer motion’ of Copernican theory is vindicated and the distorted nature of our empirical observations explained. In broadly accessible prose and by directly challenging the arguments of many stalwart defenders of Kant including Norman Kemp Smith, Henry E. Allison and Michael Friedman, Ryall’s book will be of interest to both scholars and students of Kant’s philosophy alike.