Adam Smith was confounded. One of the greatest economic and social thinkers in the history of ideas struggled with the so-called diamond-water paradox. None of us would be able to live beyond a couple of weeks without water, yet its price is relatively cheap compared to the frivolous diamond. Most people resolve this paradox by replying the supply of diamonds is scarce compared to water. But this theory lacks explanatory power. Ron and Ed will compare and contrast The Labor Theory of Value with the subjective theory of value, developed by the Marginalist Revolution of 1871-1874. The idea that all value is subjective seems obvious is retrospect, given how consumer preferences and tastes can change on a whim. Ron and Ed explore the present-day consequences for enterprise that subscribe to one or the other of these theories. They both cannot be right. The correct one is known as the First Law of Marketing: All Value is Subjective. There is value in having a correct theory of value.