Potestas essendi is a website on medieval philosophy edited by Nicola Polloni, with a particular focus on metaphysics, natural philosophy, and the history of hylomorphism. The website brings together research materials, texts, videos, teaching resources, and other tools for specialists, students, and curious readers. Much of the work centres on matter, prime matter, materiality, and the transmission of knowledge, while also opening onto broader questions in the history of philosophy.