Since the early days of antiquity, epistemology, ontology, and metaphysics are fundamental fields of philosophical inquiry. The concept of knowledge is the main topic of epistemology, whereas that of ontology and metaphysics is the concept of being. This course introduces to the students some of the main ideas and theories that are part of contemporary philosophical debates. In the first part, the concept of knowledge is introduced. Particular attention is given to the concept of justification and to the variety of viewpoints from which it could be approached. In the second part, we will examine some metaphysical problems: the-mind-body problem, personal identity, time and becoming, free will and determinism, etc.