# Symmetries in social choice theory

Elementary group theory has all sorts of surprising applications. I will show how an action of $S_n$ on the space of judgement profiles of n people, leads to an impossibility result concerning certain types of social welfare (judgement aggregation) functions. One example is that, other than unanimity, there is no reasonable democratic voting process which is also anonymous. Other amusing examples will be taken from Australian politics and high court cases. Here is how the talk will end: philosophical anarchists were right all along; refreshing tap water will be served as you exit on the left.

Since the group theory used is especially elementary, I will assume no knowledge beyond MATH1115/6. (The definition of a group will not be given during the talk and is also (probably) unnecessary/discouraged/unjust.) Therefore, first year students are especially welcome.

[Note: the location for this talk is JD101 not JD G35.]