The concept of preference dominates economic theory today. It performs a triple duty for economists, grounding their theories of individual behavior, welfare, and rationality. Microeconomic theory assumes that individuals act so as to maximize their utility – that is, to maximize the degree to which their preferences are satisfied. Welfare economics defines individual welfare in terms of preference satisfaction or utility, and social welfare as a function of individual preferences. Finally, economists assume that the rational act is the act that maximally satisfies an individual's preferences. The habit of framing problems in terms of the concept of preference is now so entrenched that economists rarely entertain alternatives.