 Tolerance of newly encountered antigens demonstrates the “fluid” state of the reactive immune repertoire that undergoes alteration over the lifespan of the organism (Grignolio et al. 2014). And with a changing “immune biography”, biological identity no longer conforms to the simple binary division of self and nonself that has hitherto characterized immune theorizing. Accordingly, animals have no immutable molecular essence that would ensure persistence of identity, at least as determined by immune tolerance or rejection (León-Letelier, Bonifaz, and Fuentes-Pananá 2019). Identity then becomes an ever-changing process of accepted transformations and rejected entries. From this vantage point, the animalist definitions of diachronic identity as a mere persistence of life or even an underlying constancy fails to account for the dynamic quality of immune-mediated identity transitions (van Inwagen 1990: 148–149; Olson 1997; Mackie 1999; Roy and Hebrok 2015; Dupré 2017). Consequently, the immune processual point of view defines organismal persistence as “a coordinated group of changes” rather than as an invariant state or a continuous connection between such states. This understanding has important implications for philosophy of biology and ontology, more generally (Dupré 2014; Nicholson and Dupre 2018; Meincke 2018).