SUMMARY: The author has analysed the most important trends in contemporary science, epistemology, history of science, technological thought, and ethics. He has also analysed the doctrine of the most important pontifical documents, from Gau-dium et Spes to Veritatis Splendor about faith, ethics, science and technology. After a rigorous comparison, his main conclusion is that: a) it is possibile to develop a va­lid Fundamental Ethics of Science and Technology, to answer to the growing que­stions of scientists and technologists all over the world; b) starting from a systemic point of view, it is possible to harmonize ethics and scientific and technological thought in order to help professionals in science and technology to be well aware and respectful of ethical needs and moral laws in their work.