“Leftists”, a distinct and meaningful group?

This article proposes a comprehensive taxonomy of the diverse types of “leftism”, grounded in historical and materialist analysis, to inform future comparative research on political systems and ideology. More specifically, it discusses (1) the taxonomic confusion over leftism and liberalism, (2) the plausible overlap between the liberal-conservative and left-right metaphors, (3) leftists as a distinct group versus liberals, (4) leftists as different groups from each other, and (5) the implications of the above for political, psychological research, and activism, in the hope of encouraging debate, advancing our understanding of social reality, and improving cooperation and conflict resolution.