This project proposes a historical and systematic study of German and French intellectual projects between 1870 and 1940 labelled 'Philosophy of Life,' 'Biological Philosophy,' and 'Philosophical Anthropology.' The core hypothesis is that they share an alternative conception of philosophy, called here heterodox naturalism, which (1) resists reductive naturalisms as well as idealist and analytical approaches, and (2) seeks to articulate an expansive notion of 'life' not restricted to that provided by the natural sciences. The project will clarify how these non-reductive conceptions of life aimed at rethinking the specificity of human beings as living entities, and were driven to articulate an alternative approach of knowledge by the institutional settings of the time. Three dimensions are focused upon: 1) their alternative conception of philosophy, requiring a meta-philosophical analysis of the positions at stake; 2) their conceptions of life, as well as their conceptions of human uniqueness to which these lead, requiring conceptual and terminological analyses; and 3) the sociological and institutional factors to which they responded, requiring a sociologically-driven analysis. The project draws upon the results of an ongoing FWO-project on “Vitalism – A Counter-History of Biology”, and purports to project, as did the latter one, its results to our current era, with attention for the place of the humanities in an academic institution mainly driven by naturalistic concerns.