Chapter 4: This chapter argues for a new way of thinking about what an ecologically oriented dialogue between theatre and science might give rise to. Three canonical Western texts – Plato’s cave, Shakespeare’s Hamlet, and Beckett’s Endgame – are read as instances of geology. The aim is to show how Western theatre is not simply a privileged space for human society to reflect on itself, as is often claimed, but a nonhuman medium, a decidedly mineralized practice – the very thing that so troubled Plato and that has caused Western philosophy to remain so suspicious of the stage. Reading Western theatre as geology, moreover, permits a theory of eco-performance criticism appropriate to and for the Anthropocene. Where accepted models of eco-theatre tend to run into dangerous contradiction, practically and theoretically, by divorcing themselves from theatre’s larger ecology and history, this chapter discloses, by contrast, the extent to which the theatrical medium is always already ecological by dint of its occluded mineralogy.