Giordano Bruno’s interest in magic was not a marginal aspect of his philosophy. In the magical works written in 1589 and 1591, Bruno carried out his project of a cultural reform, which he also conceived as a pratical renovatio. In De magia naturali Bruno undertook a careful theoretical reexamination of Renaissance magic in order to ground its "experimental data" on physical foundation. Some traditional notions , which Bruno found in his sources and made use of, are analyzed in his paper (...) to show the deep change they underwent in the light of Bruno’s new ontology and cosmology. (shrink)