This monograph tackles Marshall McLuhan's relationship with Jacques Maritain and Étienne Gilson and, thanks to unpublished letters, essays and interviews, accredits a hypothesis that, until now, has found little support in the academic community. The Canadian author's research in the mediasphere, commonly considered a direct consequence of literary studies, in reality has its roots in a philosophical and theological education that constitutes its origin and deep structure. McLuhan’s works - which deal with different fields of knowledge: communication, poetry, painting, society and technology - would represent the product of the different figures that emerge from a metaphysical background. The figure/background relationship, fundamental in McLuhan's work, is here resumed in its ontological and epistemological dynamics, producing the conditions of possibility for the definition and interpretation of reality that, ultimately, follows laws written according to linguistic metaphors. McLuhan’s relationship with the Neo-Thomist philosophers Maritain and Gilson, which lasted four decades, from the time of his doctorate in Cambridge, in the 1930s, until the end of their lives, in the 1970s, is chosen as a field of investigation to explore the paths that allowed McLuhan to start from the classical culture of the Trivium and arrive at the discovery of new disciplinary territories, from cultural studies to media studies, of which he is considered the founder. This text, in addition to following the traces scattered in the published volumes - citations, notes, bibliographies - is based on unpublished documents and primary sources that are deposited in the Library and Archives of Canada, where McLuhan's legacy is located, the Pontificial Institut of Medieval Studies, custodian of Gilson's legacy and finally the Bibliothèque Nationale et Universitaire de Strasbourg, where Le Fonds d'archives Maritain is preserved. This original work of scholarship appeals to students and researchers of these thinkers working across multiple disciplines.