In this essay, Philippe Meyer attempts to show how the most recent scientific developments have renewed traditional philosophical questions in a total and irreversible manner.One of these problems is that of perception and feeds the debate between materialism (we perceive the world that exists) and idealism (the world exists because we perceive it). He shows how the neurobiology of our visual system leads us to address the problem of visual perception in a completely new light : of course we perceive the world that exists around us, but depending on the structure of our neurovisual system, thus, in our own way.Philippe Meyer is a professor at the University of René Descartes, director of The Human and Social Sciences cursus at the Necker School of Medicine and doctor at the Necker hospital. He is the author (with P. Triadou) of Leçons d'histoire de la pensée médicale (History Lessons of Medical Thought) with Editions Odile Jacob (1996).