The basic insight of this analysis is found in Heidegger’s remark that, for the most part, the things of the world are not represented by our minds at any given moment. Mostly we fail to notice that the ground beneath our feet is stable, that our heartbeats continue without interruption, that atmospheric oxygen enables the continuation of our lives, and that the absence of political uproar in the streets makes possible our calm contemplation of phenomenological ontology. Usually, the life of things is notaccessible to us, but hidden, concealed, or withdrawn.
And here we encounter the seldom-noted ambiguity of Heidegger’s concept of the “ontological difference”: the difference, so important for his philosophy, between being and beings. On the one hand, the ontological difference means the difference between present and absent, veiled and unveiled, concealed and unconcealed, tool and broken tool, and so forth.
— Graham Harman, The Revenge of the Surface: Heidegger, McLuhan, Greenberg