Philosophy 144

Individuals in a group often have conflicting preferences between alternative courses of action, e.g., concerning the choice of a leader for the group, the choice of public policies, and so on. Moreover, actions often affect individuals differently: some may gain while others may lose, and the magnitudes of gains and losses may be unequal for different individuals. These observations lead to two of the basic questions of Social Choice Theory. First, what are good methods of group decision making in the face of conflicting preferences? Second, can we evaluate the overall social welfare of some alternative course of action in terms of the welfare of each individual in the group under that alternative?

In this class, we will study methods of voting as answers to the first question and methods of utility aggregation as answers to the second. Social Choice Theory assesses these methods using precise criteria or “axioms” that aim to capture aspects of fairness, equality, efficiency, etc. Logical reasoning is used to prove the compatibility or incompatibility of various criteria, as well as to characterize a voting or aggregation method as the unique method satisfying some criteria. Students should be comfortable with rigorous logical reasoning at the level of Philosophy 12A (Introduction to Logic).

Topics concerning voting will include: arguments for and against majority rule in two-candidate elections, including May’s Theorem; Arrow’s Impossibility Theorem; voting methods including Plurality, Instant Runoff, Borda, and Condorcet methods; the Gibbard-Satterthwaite Theorem on strategic voting; Sen’s Liberal Paradox for preferences and rights; alternatives to preferential voting, including approval voting; probabilistic voting methods or “lottocracy.” Topics concerning social welfare evaluation will include: individual utility theory; interpersonal comparisons of utility; Harsanyi’s Theorems; aggregation methods including utilitarianism, Rawlsian leximin, prioritarianism, Nash’s bargaining solution, sufficientarianism; critiques of welfarist approaches to social choice.

As taught this semester, Phil 144 satisfies the elective requirement for the logic minor.