Metaphysical realism as a pre-condition of visual perception STEPHEN J. BOULTER Field Chair for Philosophy, Westminster Institute of Education, Oxford Brookes University, Harcourt Hill Campus, Oxford, OA2 9AT, UK (e-mail: sboulter@brookes.ac.uk; phone: 01865 488566). Received 14 November 2002; accepted 28 May 2003 Key words: Anti-realism, Aristotle, Constructivism, Darwin, Evolutionary biology, Kant, Metaphysical realism, Visual perception in vertebrates Abstract. In this paper I present a transcendental argument based on the findings of cognitive psychology and neurophysiology which invites two conclusions: First and foremost, that a pre-condition of visual perception itself is precisely what the Aristotelian and other commonsense realists maintain, namely, the independent existence of a featured, or pre-packaged world; second, this finding, combined with other reflections, suggests that, contra McDowell and other neo-Kantians, human beings have access to “things as they are in the world” via non-projective perception. These two conclusions taken together form the basis of “Aristotelian” metaphysical realism and a refutation of the neo-Kantian “two-factor” approach to perception. 1 Introduction Kant is famous (or infamous) in philosophical circles for having maintained that external objects as we know them do not exist independently of us but only in virtue of our imposition of concepts and a spatio-temporal setting upon what he argued must be a phenomenal chaos received via sensation. 2 This revolutionary claim was in large part a response to Humean scepticism, itself a direct descendent of Locke’s representative realism which acknowledged a gap between what is perceived (allegedly an internal sense impression or sense datum) and the object of knowledge (the object in the external world). To speak somewhat loosely, to close this gap and eliminate the possibility of scepticism, Berkeley brought the external world into the mind, thereby adopting a form of idealism. Kant rejected this approach and instead took the mind out into the world, thus acknowledging an external world populated by physical objects, but at the cost of rendering its features dependent upon the ordering mind. 3 In the twentieth century representative realism has become less and less popular as a theory of perception. This is in no small part due the heavy criticism levied at the arguments traditionally used to support the existence of sense data. 4 There are also few takers for Berkeley’s brand of idealism. But Kant has fared substantially better. There are many contemporary anti-realists who take their inspiration from © 2004 Kluwer Academic Publishers. Printed in the Netherlands. Biology and Philosophy 19: 243–261, 2004.