In this article, we describe an ontology aimed at the representation of the relevant entities and relations in the philosophical world. We will guide the reader through our modeling choices, so to highlight the ontology’s practical purpose: to enable an annotation of philosophical resources which is capable of supporting pedagogical navigation mechanisms. The ontology covers all the aspects of philosophy, thus including characterizations of entities such as people, events, documents, and ideas. In particular, here we will present a detailed exposition of the entities belonging to the idea branch of the ontology, for they have a crucial role in the world of philosophy. Moreover, as an example of the type of applications made possible by the ontology we will introduce PhiloSurfical, a prototype tool we created to navigate contextually a classic work in twentieth century philosophy, Wittgenstein’s Tractatus Logico-Philosophicus. We discuss the potential usage of such navigation mechanisms in educational and scholarly contexts, which aim to enhance the learning process through the serendipitous discovery of relevant resources.