This book reconstructs, both from the historical and theoretical points of view, Leibniz’s geometrical studies, focusing in particular on the research Leibniz carried on in the last years of his life. The main purpose of the work is to offer a better understanding of the philosophy of space and in general of the mature Leibnizean metaphysics, through a pressing confrontation with the problems of geometric foundation. Regarding this scope of problems, the book also deals quite in depth with Leibniz’s theory of sensibility, thus favouring the comparison and contrast between Leibniz’s philosophy and Kant’s transcendentalist solution. The Appendix gives editing to a number of previously unpublished manuscripts on geometry from the Leibniz Archiv.