Three important concepts discussed in the Three Dialogues are perceptual relativity, the conceivability/master argument, and phenomenalism. Perceptual relativity argues that the same object can appear to have different characteristics depending on the observer's perspective. Since the objective features of objects cannot change without an inherent change in the object itself, the shape must not be an objective feature. In his foundational work, Berkeley foreshadows the philosophical impact of twentieth-century physics, which challenges the foundations of materialism and calls for a better understanding of both the physical and the mental aspects of reality.