Harman's Tool-Being radicalises Heidegger's tool-analysis by extracting from it an ontology of objects rather than a phenomenology of human use. The iconic idea is withdrawal: objects never coincide with their relations, appearances, functions or human access to them. Harman's theoretical contribution is to relocate the primary ontological gap away from the modern divide between subject and world and toward the tension between objects and relations as such. The book's operation is exegetical and metaphysical: it rereads readiness-to-hand as a general structure of hidden reality, extending beyond hammers, users and practical activity to every entity in the cosmos. This allows substances to return without collapsing into either physical particles or linguistic effects. The bridge to the wider field is object-oriented philosophy, speculative realism and post-Kantian metaphysics. Tool-Being makes the thing once again philosophically active, autonomous and resistant to exhaustive translation into knowledge, utility or representation.