Not many seminal works of philosophy are the product of an unoccupied mind in the midst of a failed mining project, but that, it seems, was the story behind Leibniz’s Discourse on Metaphysics . At the beginning of January 1686, he travelled to the Harz mountains to continue his (ultimately ill-fated) project to improve the productivity of the mines there via wind machines and water pumps of his own invention. When the work stalled for a few days, Leibniz did what he did best: he thought. At the
