Philosopher, economist, historian. Called "Saint David" by some friends, he courageously expounded atheism while leading an exemplary life devoted to the pursuits of truth and of friendship. In addition to developing perhaps the most important philosophical defense of empiricism (knowledge gained from the interplay of our senses and mind), he was also a friend and mentor of Adam Smith and one of the principal founders of modern economics. Among his many scandalous ideas was the admonition that we cannot derive an "ought" from an "is." This meant that morals were not only severed from the "authority" of religion. They could not be conclusively regrounded in either fact or logic. Kant strongly disagreed with this and tried to reground morals to logic.