This paper explores how theoretical, practical and political issues are addressed differently by cost - benefit analysis and deliberative - participatory approaches to environmental policy. Theoretically rigorous approaches may prove to be too narrowly defined and so unsuitable because they neglect the requirements of practical implementation. Yet pragmatism which flaunts theoretical understanding lacks analytical power and can mislead policy. How economic methods, such as contingent valuation, compare with those from political science, such as citizens' juries, is an open question which we attempt to address. In addition, the new hybrid approach of deliberative monetary valuation is critically reviewed. A comparison of these approaches is made which draws out the difficulties of developing practical policy tools which are theoretically grounded and avoid political manipulation.