Could it be rational to believe contrary to the evidence if the belief brings a substantial amount of practical benefits? In my thesis, I investigate this question through the lens of social choice theory. Specifically, I argue that it is never rational to believe contrary to the evidence by utilizing Arrow’s impossibility theorem. To this end, I introduce an analogy between a belief system and a social group, discuss certain conditions that hold in a rational agent’s belief system, and compare and analyze the performances of different belief systems. The goal is to shed light on the role of evidence in a rational agent’s belief system while exploring the application of theoretical results in social choice theory to the ethics of belief.