There is a growing literature on climate-policy mixes, much of which relies on ad hoc criteria and framings. A widespread, often implicit, assumption in this literature is that policy performance improves as more instruments are used. This lecture synthesizes existing approaches by systematically assessing their underlying criteria and rationales. It identifies policy-mix arguments distinguished by their focus on market failures, instrument synergies, multiple objectives, distinct policy levels, sector-specific challenges, intertemporal considerations, systemic coverage and effects, and policy processes. A comparative assessment is undertaken of the implications of these approaches for the policy mix, highlighting consistency, complementarity and incoherence. For balance, arguments in favour of keeping policy mixes simple are also considered, with particular emphasis on transparency, adaptive flexibility and international harmonisation. Finally, the links between policy-mix features and political feasibility are explored. The findings inform the formulation of an integrated framework and a set of guiding principles for designing climate-policy mixes.