While economic theory in general may be defined as the theory of how an economic condition or an economic development is determined within an institu… - Kenneth Arrow

I want, however, to conclude by calling attention to a less visible form of social action: norms of social behavior, including ethical and moral codes. I suggest as one possible interpretation that they are reactions of society to compensate for market failures. It is useful for individuals to have some trust in each other's word. In the absence of trust it would become very costly to arrange for alternative sanctions and guarantees, and many opportunities for mutually beneficial cooperation would have to be, foregone.

The incompleteness of property rights in general creates well-known problems in welfare economics, being in fact the basic component of externalities. In particular, markets for future commitments are relatively under-developed compared with those for the present or immediate future. Individuals have to supply for themselves expectations as to future developments in order to make decisions with consequences extending into the future, e.g., investments. These expectations, for example of prices or of supply availabilities, are not "property," but they influence the use of property and are taken into account in the present legal system. For example, an obligation to sell a product for the next few years at a given price is understood in the law to hold only if conditions do not change in a strongly unexpected way; this understanding does not require explicit statement.

The problem of interpersonal comparison of utilities seems to bother economists more than philosophers. As already indicated, utility or satisfaction or any other similar concept appears in economic theory as an explanation of individual behavior, for example, as a consumer. Specifically, it is hypothesized that the individual chooses his consumption so as to maximize his utility, subject to the constraints imposed by his budget. But, for this purpose, a quantitatively measurable utility is a superfluous concept. All that is needed is an ordering, that is, a statement for each pair of consumption patterns as to which is preferred.