The present work is dedicated to theoretical aspects of long-term evaluation with a focus on time and uncertainty structure. Motivated along the lines of global warming, the analysis renders contributions to the fields of environmental economics, decision theory, the economics of sustainability and cost benefit analysis. The thesis is structured in three parts. The first part examines the relation between the concepts of weak and strong sustainability and the weight given to future consumption. The second part introduces a generalized evaluation model and a new concept of risk aversion. The latter concept, termed intertemporal risk aversion, takes up an important concern of the precautionary principle. The third part extends the underlying model and analyzes the interaction with other characteristics of intertemporal decision making. The latter include an implied preference for the timing of uncertainty resolution as well as different stationarity assumptions.The first part of the thesis relates to the sustainability debate and the concepts of weak versus strong sustainability. While the advocates of the weak sustainability concept consider man made goods and capital a fair substitute for environmental goods and capital, the advocates of the strong sustainability concept judge such substitutability as highly limited. I show in a stylized growth model, how social discount rates generally fall for a weak sustainability specification of welfare, while they grow for a strong sustainability specification. It turns out that under the given assumptions a strong sustainability specification of welfare implies a lower weight given to future consumption streams than a weak sustainability specification.The second part of the thesis introduces the concept of intertemporal risk aversion in a didactically simplified two period framework. The concept takes up an important concern of the precautionary principle regarding a higher willingness to undergo preventive measures in order to avoid a threat of harm. I show that the concern is substantiated as well by von Neumann Morgensterns widespread axioms for choice under uncertainty when carefully integrated into a temporal setting. In such a generalized framework, the standard model of intertemporally additive expected utility corresponds to intertemporal risk neutrality. In contrast to the classical concept of (atemporal) risk aversion, the concept of intertemporal risk aversion can be applied immediately to the multi-commodity setting. For the one commodity special case, the concept closely relates to the attempts of disentangling atemporal risk aversion from intertemporal substitutability.The third part of the thesis extends the model to an arbitrary finite time horizon with generalized preferences and elaborates the corresponding axiomatic and functional characterizations of intertemporal risk aversion. Moreover, I identify different assumptions that allow to simplify the model structure. On the one hand, these assumptions are concerned with a stationary evaluation of certain and uncertain consumption plans. On the other hand, they relate to a deduced preference for the timing of uncertainty resolution. The resulting simplifications allow to characterize intertemporal risk aversion in a single parameter, as well as to disentangle atemporal risk aversion from intertemporal substitutability in a non-recursive evaluation structure. Finally, I show that a normatively motivated combination of the assumptions implies that a time consistent, intertemporal risk averse decision maker has to choose a zero rate of pure time preference. Instead of devaluing the future for reasons of sheer impatience, such a decision maker is only allowed to give reduced weight to future welfare if uncertainty increases over time. The major implications of the present work can be divided into two fields. The first field relates to the sustainability debate and the evaluation of the long run. In this regard, the analysis in the first part of the thesis shows that the characterization of weak and strong sustainability through the degree of substitutability between environmental and produced goods stands in a surprising and possibly unwanted relation to the sustainability demand in the sense of a stronger commitment to future consumption streams. The analyses carried out in the last part of the thesis implies that a zero rate of pure time preference cannot only be founded on moral considerations, but also on assumptions concerning a time consistent evaluation of uncertainty. The second field of implications concerns the handling of uncertainty. In particular, the concept of intertemporal risk aversion mediates between the advocates and the opponents of the precautionary principle. On the one hand, it takes up the concern regarding a higher willingness to undergo preventive action than implied by the standard model. On the other hand, intertemporal risk aversion formalizes this concern and reconciles it with the standard assumptions underlying economic evaluation. That way, it encounters the critique of the precautionary principle as being vague, arbitrary and, thus, paralyzing.