Complex images of the differences between public and private activities are endemic in modern capitalist societies. Numerous examples can be found in the field of social policy, but this paper focuses on the historical dialectic between public and private pension arrangements. It compares the interaction over time in a number of countries of the central principles of solidarity and equivalence which have shaped the development of pension provision. Then it illustrates how an understanding of contemporary pressures for the privatization of pension arrangements as a response to the fiscal crisis of welfare states cannot be divorced from their historical and institutional contexts. The paper concludes that pluralistic pension systems offer the best prospect for rational policy analysis and debate provided that a continuing critique of, and dialogue between, the different sectors is encouraged to flourish.