This text introduces a new approach to the issue of radical scientific revolutions, or paradigm-shifts, given prominence in the work of Thomas Kuhn. The book articulates a dynamic and historic version of the conception of scientific a priori principles first developed by the philosopher Immanuel Kant. Focusing on the development of scientific philosophy from Kant to Rudolf Carnap, along with the developments within science at the same time, the author provides a dynamic conception of relativized a priori principles. This idea within the physical sciences aims to show that rational intersubjective consensus is intricately preserved across radical scientific revolutions or paradigm-shifts and how this is achieved. This book defends the Enlightenment ideal of scientific objectivity and universality while also doing justice to the revolutionary changes within the sciences that have undermined Kant's original defense of this ideal.