The usual economic evaluation of future costs and benefits gives very little importance to what happens in one century and after. This does not square well with our collective concern for the long-term future of humanity at a time of mounting environmental, social and political crises. Is the economic approach fundamentally flawed? Do “dismal theorems” justify throwing away standard cost-benefit analysis? This lecture will revisit the underpinning normative concepts of evaluation of growth paths and long-term uncertainty.