That human knowledge is a double-edged sword is a very old idea. In Plato's Republic we find Socrates formulating the question, "Is it not true that he who knows how to guard against disease is also most able to infect with it and escape detection?" (333e). This is one of the first expressions of the problem concerning the moral responsibility of people who possess some kind of knowledge or expertise. Actually, the Greeks not only revealed the close relationship between ethics and applied knowledge, but they also tried to solve that problem by requiring that students of medicine follow the Hippocratic Oath. ¹