Yesterday afternoon I went to a seminar in Sociology given by Erik Olin Wright. His subject was 'real utopias' and he introduced it by saying that the exploration of such alternatives was a central task of emancipatory social science. Emancipatory: involving a commitment to the elimination of oppression and to creating the conditions for human flourishing. Science: that the project should be based on systematic knowledge, empirically grounded. Social: that emancipation depends on a transformation of the social world, not just of the the inner self. Erik went on to ways of thinking about alternatives, and the distinctions between desirable, viable and achievable alternatives. So much from notes I took during the seminar.
Some of the rest of what he said can be pursued here [pdf] since he was presenting what is evidently an updated version of the same paper. The basis for claiming that we need to look for alternatives to capitalism included (from my notes again, though there is a similar list in the paper linked to) that capitalism perpetuates eliminable forms of human suffering, blocks human flourishing, perpetuates deficits in individual freedom and autonomy, violates liberal principles of social justice, is inefficient, is environmentally destructive, and limits democracy.
One thing: in encouraging us to think in a hard-headed way about alternatives to capitalism, Erik uttered not a single word of apologia for the Stalinist experience, thereby showing that to think about historical alternatives doesn't require this - even though talk of alternatives is sometimes accompanied by it, as if it did.