Abstract
Social dilemma is denoted by the situation where equilibrium social state is not Pareto-efficient. Therefore, to solve social dilemma is to find a theory which maps any initial conditions to Pareto-efficient social states. However, such a theory never exists when we assume the liberty of individuals. As Sen's Liberal Paradox proved, Pareto-efficiency contradicts liberty. This theorem asserts that social dilemma is the dilemma of liberty and efficiency, not the problem of isolated decision as it has been believed. If we require individuals' liberty, then no social choice can avoid social dilemma.
