THE tradition in microeconomic theory is to take wants and technology as givens and to proceed from these to deduce from the assumption of scarcity testable implications and normative propositions. These assumptions, together with variety in tastes and abilities and differences in the number of rivals, give rise to most economic laws. In this way, laws such as those that relate to demand, comparative advantage, equalization of factor returns, and the relationship of price to cost are deduced. The role of property rights is not explicitly dealt with in this approach. But imbedded in the whole process is a third class of given datum. There must be assumed a set of social arrangements which define ownership. In this paper, I will examine some aspects of property rights that bear both on issues to which we have been led by the traditional approach and to some which we have ignored because property rights have not been treated explicitly. An example will make clear the necessity of assumptions about social arrangements. Consider the two economic laws which state that (1) demand curves are negatively sloped and that (2) queues will tend to be eliminated by a price that is free to fluctuate. The first law is true even if ownership does not include the right to buy or sell; it does not even depend on the existence of exchange. Thus, from the first law it follows that an increase in the unpleasantness of my neighbor (an increase in the price of association) will diminish the frequency of my visits. Nothing is bought or sold but the law holds true.