In the introductory part of the paper, we outline the position of the philosophy of physics in the context of naturalistic theoretical philosophy. The main message here is an appeal for understanding philosophy as an integral part of the scientific investigation of the world. In the following sections, we identify three central aspects of contemporary fundamental physics, knowledge of which is essential for philosophical reflection on physics. This is followed by an explanation of one of these aspects, which is the gauge principle. Based on classical electrodynamics, we explain with the help of a relatively modest mathematical apparatus the key idea of gauge symmetry, as it appears in the core theories of the standard model of elementary particles. In the final part, we point out the philosophical relevance of the gauge principle, especially within the current debates between substance- and structure-oriented philosophies of physics.