I argue that the use of a social discount rate to assess the consequences of climate policy is unhelpful and misleading. I consider two lines of justification for discounting: (i) ethical arguments for a ‘pure rate of time preference’ and (ii) economic arguments that take time as a proxy for economic growth and the diminishing marginal utility of consumption. In both cases I conclude that, given the long time horizons, distinctive uncertainties, and particular costs and benefits at stake in the climate context, discount rates are at best a poor proxy for the normative considerations they are meant to represent.

A common justification offered for unequal pay is that it encourages socially beneficial productivity. G. A. Cohen famously criticizes this argument for not questioning the behaviour and attitudes that make those incentives necessary. I defend the communal status of incentives against Cohen's challenge. I argue that Cohen's criticism fails to appreciate two different contexts in which we might grant incentives. We might grant unequal payment to someone because they demand it. However, unequal payment might be an offer instead. I claim that incentives as offers promote the ideal of society as a cooperative venture for mutual advantage.

This article surveys the debate over the social discount rate. The focus is on the economics rather than the philosophy literature, but the survey emphasizes foundations in ethical theory rather than highly technical details. I begin by locating the standard approach to discounting within the overall landscape of ethical theory. The article then covers the Ramsey equation and its relationship to observed interest rates, arguments for and against a positive rate of pure time preference, the consumption elasticity of utility, and the effect of various sorts of uncertainty on the discount rate. Climate change is discussed as an application.

Several areas of welfare economics seek to evaluate states of affairs as a function of interpersonally comparable individual utilities. The aim is to map each state of affairs onto a vector of individual utilities, and then to produce an ordering of these vectors that can be represented by a mathematical function assigning a real number to each. When this approach is used in intertemporal contexts, a central theoretical question concerns the rate of pure time preference, i.e. the evaluative weight to be applied to utility coming at different times. This article criticizes the standard philosophical account of pure time preference, arguing that it ascribes to economists a methodological commitment they need not accept. The article then evaluates three further objections to pure time preference, concluding that it might still be defensible under certain circumstances. I close by articulating a final argument that, if sound, would constitute a decisive objection to pure time preference as it currently figures in much intertemporal welfare economics.