The seminar takes its point of departure from John Carpenter’s apocalyptic horror film, The Thing (1982) in order to stage a collision between Martin Heidegger’s and Jacques Lacan’s different approaches to the question: what is a thing? In Carpenter’s film, the thing names an alien creature that is essentially formless, existing through the appropriation of the form of other beings. Conceived abstractly, Carpenter’s film poses the problem of the thing as an essentially deceptive being: a presence whose lack of identity can only be met with a correspondingly radical distrust in the appearance of things that serves to ultimately unravel the moral fabric that binds the community of Antarctic researchers. Lacking a form of its own, a purely mimetic being, the thing designates that which effaces the difference between the alien and the familiar, inhuman and human, being and appearance, figuring an enigmatic entity which can no longer be conceived or determined in terms of what it is: i.e., an essence. Through close readings of passages from Heidegger’s essay, The Thing (Das Ding), and Lacan’s Seminar VII, The Ethics of Psychoanalysis (1959-1960), we shall consider how it is possible to think that which lacks a determinate form, an essence, but is nevertheless not nothing.