 Third, although individuals may in general be the best judges of their own interests, they may not always judge wisely. This creates a disjunction between the perception of their interest and their “real” interest. Since the “public interest” is a fictitious entity which represents nothing more than the aggregate of individual interests (1970, 12), an effective legislator must have a fairly accurate understanding of the interests of those individuals that constitute the community, of what will motivate them to act in the desired ways (especially in criminal law). But if people incorrectly perceive their interests, then the legislator may be misled in constructing the appropriate motivation. Clearly, the knowledge needed by the legislator (in order to be effective in constructing adequate motives to direct individual actions) is of people’s apparent interests, while the legislator’s objective is to further their “real” interests, that is, what they would choose if they were fully rational and informed. This means that assessing the value of the constituent elements of interest (pains and pleasures) is a tricky business for the legislator; he must accurately observe the ways people behave, deduce the motives behind their actions, and encompass this knowledge in the sanctions of law. Yet these same observations of human behaviour may not also be reliable guides to the “real” interests of individuals, which must be determined on other grounds. This is why some modern day utilitarians focus on “preferences”, that is on the subjectively expressed opinion of the individual as to what she thinks will be pleasurable or painful (see Bykvist 2013).