In this article, I address the multiplicity of “posthumanisms” including posthumanism as a periodizing gesture, a description of what follows humanism; as a problematique or“ predicament”; and as a move that heralds something else—a “critical” posthumanism, a “technophilic” or “animaphilic” decentering of the human into a networked entanglement of substances, or a “posthumous” post-posthumanism. Comparing posthumanism to previous“ posts” including postmodernism, I argue that its nature as a“ post” means that posthumanism cannot avoid the“ postal system” described by Jacques Derrida, whereby discursively constituted goals fail to reach their intended destinations. Drawing upon a process-relational conception of the human (and of the cosmos), I argue that the human has never been human such that it can be overcome or transcended. Our humanity is always ever in process, which means that any posthumanity will always be unstable and always tied to the realm of “alternative humanisms.” There is, however, one form of posthumanism that is worth conceiving as such: this is posthumanism, the“ close encounter of the third kind” where by we humans contend with our ultimate erasure, that of extinction.