Not all truths are on a par. The realm of truths is structured: some propositions are only true because others are. The relation that endows the realm of truths with this structure is often called grounding. Grounding has achieved much attention in 21st century metaphysics, but the topic is arguably as old as philosophy itself. This becomes apparent when investigating the works of the 19th-century philosopher Bernard Bolzano, who developed what is perhaps the first comprehensive theory of grounding, drawing on a rich tradition that goes back to Aristotle's Posterior Analytics. Roski's book provides, for the first time, a comprehensive study of Bolzano's theory of grounding in its entirety, paying more attention than previous studies to the interaction between grounding and the consequence-relation of deducibility.

Stefan Roski ist wissenschaftlicher Mitarbeiter am Philosophischen Seminar der Universität Hamburg.