This article searches for a way of theorizing the interconnectedness of processes of individuation, relationality and affect, with the aim of clearing the ground for an approach that establishes the basis of this interconnectedness by reference to mechanisms common to all living things. It establishes a number of shifts that enable us to think the categories and concepts like the individual, the subject, the group, the threshold, relationality, co-implication and so on according to a fundamental decentring, finally breaking with both (...) subject-centredness and its privilege of the individual as model or starting point; the same epistemological shift implies the rejection of the anthropocentric divide between humans and animals, while avoiding species of sociobiologism, pre-formationism, geneticism and other monocausal paradigms. What the new problematic of life enjoins us to rethink are the standpoint of singularity rather than that of the individual, coupled to the standpoint of relationality as a principle enabling us to think the self—other, human—animal, nature—culture and human—world in terms of compossibility and complex becoming. This view about the co-constitution of all life has major implications regarding responsibility for the other and responsibility for the world, grounded in the standpoint of the temporality and historicity of being as existential condition circumscribing the relation to the other. This shift at the level of ontology is explored via an engagement with the work of Simondon and his conceptual apparatus, particularly ideas of psychic and collective individuation, the pre-and transindividual, the associated milieu; this perspective is re-articulated by way of the work of Merleau-Ponty, Haraway’s notion of ‘companion species’, Ettinger’s concept of the ‘I—other plurality’, and cognate concepts that point to a new terrain for theorizing affect. (shrink)