This work is concerned with the problems of whether a utility concept that is cardinal, in so far as ratios between utility differences are significant, exists or not and whether it is useful, e.g. in creating testable models of behaviour, or whether a merely ordinal preference function will do for all purposes. Some selected highlights from the debate between cardinalists and ordinalists are analyzed, but essentially this is a presentation of fresh elements in the case for cardinalism. Special themes analyzed include the distinction between utility and risk attitude, motivating decisions under uncertainty, multiperiod allocations and complementarity. Empirical evidence is presented and it seems that attempts at measuring utility give amazing results. The book should interest researchers, teachers and some advanced students in economics, economic psychology, welfare theory and themes concerned with human behaviour.