Rooted in late seventeenth-century theories of rights, liberal ideas have brought forth since the nineteenth century a full-edged complex of traditions in moral, political, economic, social, and legal thought. Yet in historiographical debates such complexity is often blurred by presenting it under the uniform terms of a canon. Along with other methods, conceptual history is contributing to the rediscovery of liberalism's diversity. This group of articles compiles three conceptual studies on scarcely explored aspects of the history of liberalism in Denmark, Finland, and Hungary—countries whose political past has only occasionally figured in mainstream accounts of European liberalism. This introductory article is a methodological discussion of the rationale and forms in which liberalism's historical diversity is rendered through comparative conceptual research. After reflecting on the limits of the Anglophone history of political thought to grasp the plurality of liberal traditions, the article examines how transnational conceptual histories recast the understanding of liberalism as a concept, theory, ideology, and political movement.