The foundations of multi-attribute utility theory are reviewed and compared with the author's practical experience and other psychological studies of decision-making. The case is presented for a new approach to decision-making, moving away from the strictly numerical techniques. Instead of concentrating on the normative or descriptive aspects of decision-making, themed-problem of decision-making is studied, thereby giving the decision-maker more control over the decision-making process and ensuring a more truly participative approach to design and decision-making. The problem of uncertainty is also tackled by considering it from both the stochastic and fuzzy standpoints. A revised approach to the assessment of uncertainty and its incorporation in the decision-making process is advocated. The theoretical framework behind these ideas is expressed using fuzzy set theory. Previous attempts to apply fuzzy set theory to multi-attribute decision-making are reviewed and criticised for their failure to tackle the basic assumptions of multi-attribute utility theory. A practical methodology for using verbal descriptions is derived, and illustrated with a worked example. A practical description of how to apply the method is included, and the results of some applications are presented.