DEUT394 In early 1990s, one of the great medical research exercises of modern times took place. It became known as the Nun Study.… Researchers were able to test whether their emotional state in 1930 had an effect on their health some sixty years later.… The results… were startling. The more positive emotions – – contentment, gratitude, happiness, love, and hope--the nuns [had] expressed in their [1930] autobiographical notes, the more likely they were to be alive and well sixty years later… So remarkable was this finding that it has lead, since then, to a new field of gratitude research, as well as a deepening understanding of the impact of emotions on physical health. What medicine now knows about individuals, Moses knew about nations. Gratitude – – hakarat hatov – – is at the heart of what he has to say about the Israelites and their future in the Promised Land.… This is what he warned: [verse 11-this verse]. The worst thing that could happen to them, warned Moses, would be that they would forget how they came to the land, how God had promised it to their ancestors and taken them from slavery to freedom, sustaining them during the forty years in the wilderness. This was a revolutionary idea. The nation's history, it asserted, should be engraved on people's souls and re-enacted in the annual cycle of festivals; the nation, as a nation, should never attribute its achievements to itself--"my power and the might of my own hand"--but should always ascribe its victories, indeed its very existence, to something higher than itself: God. This is a dominant theme of Deuteronomy, and it echoes throughout the book time and again.