In this essay we explore systematically the general equilibrium implications of endogenous fertility for some of the social issues of population policy, including the optimal level or rate of growth of population, real and false externalities, and issues of inter- and intragenerational income distribution. Endogenous fertility simply means that parents care about the numbers and welfare of their children and respond to economic constraints and opportunities in their choices affecting their children and/or that parents bear children as a provision for old age security. It is remarkable that this simple and obvious concept has such far reaching and significant normative implications. What is even more remarkable, however, is that the idea that parents care about their children does not seem to have found any place in the current ethical and philosophical debates about optimal population.