 The category of Stuff is still under-developed, and seems to be where the category Event was decades ago. Stuff and stuff-talk represent either (i) an important ontological category, which remains poorly understood, or, (ii) a distinct way of conceiving or talking about objects, where its interface with object-talk is, again, poorly understood. In the absence of consensus on the referents and logico-linguistic mechanics of mass expressions, controversy about stuff is bound to continue.