I discuss Agazzi's contribution to the philosophy of physics, a discipline introduced in Italy by his groundbreaking treatise of 1969. At a variance with the neopositivistic philosophy, dominant at the time, which appeared concentrated almost exclusively on a formal analysis of scientific languages, he showed that the philosophy of physics should discuss the logical foundations and the epistemological implications of physical theories, addressing also the issues of philosophy of nature, such as the reality and the structure of physical objects, the subject/object relationship, and the role of causality principle. Here I focus on the ontological question of the wave-particle duality, considered by the neopositivistic perspective of the standard interpretation as a metaphysical pseudoproblem. Agazzi, on the contrary, identified it as the new and fruitful experimental evidence from which quantum mechanics originated, as the theory that unified at the elementary level the classical concepts of matter and radiation. I argue that in this way he gave an essential contribution also to the debate on the foundations of quantum mechanics. His ideas, and in particular his appeal to the introduction of new and completely non classical concepts, inspired and influenced certain nonstandard realistic interpretations.