Discussions of impact assessment and evaluation are the newest installment in the brief history of the field of transitional justice. Noticeably, a positivist logic of inference is being favored in these discussions. This article argues that a distinction should be made between impact assessment and evaluation, and that the role of positivist approaches is best conceived of as contributing to the former. Evaluation, on the other hand, should be undertaken by those analysts willing to embrace and promote normative ideals, to which they compare practices on the ground. This type of 'comparison to the ideal' is the province of interpretive-critical logics of inference. After carving out a modest role for positivism, the article presents a quantitative analysis of transitional justice impact to show how such a logic is good for grounding observers' expectations for different types of transitional cases. The analysis demonstrates that transitional justice mechanisms do not have a uniquely destabilizing effect across such cases. The article concludes with a syncretist view - that interpretive, ideal-based evaluations should proceed alongside positivist impact assessments.