In this essay, I critically engage with a methodological approach in contemporary political theory — unconstrained utopianism — which holds that we can only determine how we should live by first giving an account of the principles that would govern society if people were perfectly morally motivated. I provide reasons for being skeptical of this claim. To begin with I query the robustness of the principles unconstrained utopianism purportedly delivers. While the method can be understood as offering existence proofs, because we can devise other situations in which morally flawless decision making would unearth alternative sets of principles, I argue that such proofs tell us surprisingly little about how we should live in general. Drawing on this point, I contend that normative models that wish away certain phenomena that are uncontroversially central to any account of politics cannot plausibly claim to tell us how we should live in political society. I conclude by offering a more positive sketch of why avoiding this brand of utopianism might not represent a problematic capitulation to the morally nonideal and suggest that theorizing in light of certain constraints may be a precondition of good normative theorizing itself.