The philosophical debate at the heart of critical realism (CR) concerns the legitimacy of the mode of reasoning that it employs to reach its ontological conclusions: the transcendental argument (TA). This form of argument was most famously introduced to philosophy by Immanuel Kant in the Critique of Pure Reason, marking, as it were, the dawn of the modern era of philosophy in the (anti-) Copernican Revolution (Kant 1781/1953); just as Copernicus unseated ‘man’ from the centre of the universe with his heliocentric astronomy, so too Kant effected a similar blow to anthropocentrism by recentering the project of philosophy around the (self-)understanding of humanity and its world, rather than a metaphysics of reality per se.