 As this passage suggests, what Kant has changed in the Critique is primarily his view about the role and powers of the understanding, since he already held in the Inaugural Dissertation that sensibility contributes the forms of space and time – which he calls pure (or a priori) intuitions (2:397) – to our cognition of the sensible world. But the Critique claims that pure understanding too, rather than giving us insight into an intelligible world, is limited to providing forms – which he calls pure or a priori concepts – that structure our cognition of the sensible world. So now both sensibility and understanding work together to construct cognition of the sensible world, which therefore conforms to the a priori forms that are supplied by our cognitive faculties: the a priori intuitions of sensibility and the a priori concepts of the understanding. This account is analogous to the heliocentric revolution of Copernicus in astronomy because both require contributions from the observer to be factored into explanations of phenomena, although neither reduces phenomena to the contributions of observers  alone.[6]  The way celestial phenomena appear to us on earth, according to Copernicus, is affected by both the motions of celestial bodies and the motion of the earth, which is not a stationary body around which everything else revolves. For Kant, analogously, the phenomena of human experience depend on both the sensory data that we receive passively through sensibility and the way our mind actively processes this data according to its own a priori rules. These rules supply the general framework in which the sensible world and all the objects (or phenomena) in it appear to us. So the sensible world and its phenomena are not entirely independent of the human mind, which contributes its basic structure.