The non-existence of all things; a concept that can be frightening, fascinating, or dismissed as the product of the logical confusion of treating the term ‘nothing’ as itself a referring expression instead of a quantifier. This confusion leads the unwary to think that a sentence such as ‘nothing is all around us’ talks of a special kind of thing that is all around us, when in fact it merely denies that the predicate ‘is all around us’ has application. The feelings that lead some philosophers and theologians, notably Heidegger, to talk of the experience of Nothing, is not properly the experience of nothing, but rather the failure of a hope or expectation that there would be something of some kind at some point. This may arise in quite everyday cases, as when one finds that the article of furniture one expected to see as usual in the corner has disappeared. The difference between existentialists and analytical philosophers on the point is that whereas the former are afraid of Nothing, the latter think that there is nothing to be afraid of. A rather different set of concerns arises when actions are specified in terms of doing nothing: saying nothing may be an admission of guilt, and doing nothing in some circumstances may be tantamount to murder (see acts/omissions doctrine, trolley problem). Other substantive problems arise over conceptualizing empty space and time.