We pass judgment on the value of scientific results. For example, we may feel that the periodic table of elements is of greater significance than the understanding that hydrogen is lighter than oxygen. For one thing, the latter fact may be deduced from an understanding of the periodic table. In this way, we may ascribe a measure of quality to an idea. The quality of an idea is subjective, and cannot be assigned an absolute value. However, it is possible to give a partial ordering and claim that idea A is of higher, lower, or equal worth in relation to idea B. The judgment of the relative importance of ideas is made routinely, for example, by an instructor in delivering a lecture or writing a book. The assignment of value occurs implicitly in the selection of topics and their relative emphasis. Once we admit a preference ordering among ideas, we may also assign an arbitrary numerical scale to them. This practice is standard in the field of economics, where a preference ordering among goods suggests a measure of utility. Since each consumer has individual tastes and needs, the resulting utility function varies from one person to another even for the same basket of goods. Further, the preferences are subjective and relative, rather than absolute. As a result, the level of utility can be based only on a conceptual scale. The basic measure of utility is an arbitrary unit called a util. In a similar way, we may assign a quality metric in terms of a granular unit of a qual. A person may assign a particular set of quals to a portfolio of ideas based on his own tastes and predilictions. A second person may offer a completely different set of quality values. This conception of an individual ordering of ideas is consistent with the view of difficulty and creativity as relative rather than absolute parameters. To pursue this line of reasoning, we may also speak of the combined quality of two or more ideas. The value of a set of ideas may be greater than, equal to, or less than the sum of the individual values.