What is immunology? Immunologists would say that immunology is the scientific attempt to understand, explain and predict immune behaviour. Nonetheless how science is defined and what is it that makes immunology a science are not trivial questions. The reason why answering these questions is philosophical, rather than scientific, relates to the fact that there are assumptions implicit in scientific inquiry that can only be uncovered from an outside perspective. Many scientists today take little interest in the philosophy of science, it is a consequence of the increasingly specialized nature of science, and of the polarization between the sciences and the humanities that characterizes much modern education. This work refers to Immunology. The immune system has a prominent position in biomedical sciences because it concerns: cell survival rules, organismic physiology, and homeostasis. The epistemology of immunology addresses, e.g., the theory of knowledge and seeks to answer the question of how knowledge occurs/ is constructed in immunology. Immunology needs foundations, truth assumptions and coherence. And the philosophy of science, looking from the outside, can help with this systematization. Historically, sciences and the philosophy of sciences have gone hand in hand. They could, together, be the intellectual affair of a single thinker. Today, complexity requires teamwork.