Many authors have written, from different approaches, about the relationships between ethics and science. In this work, we analyze how Mariano Artigas (a physicist, philosopher, and priest) did it. He gives great importance to ethics, which he considers a philosophical presupposition of scientific activity. A detailed analysis of his work allows to understand to what extent ethics is important for science. Specifically, we consider (1) the relationships of ethics with humans and with science; (2) the inter-weaving and the distinction between both of them; (3) the importance of ethics as a hermeneutical key in Popper; (4) and the emergence of ethics before, during, and after scientific activity.