Metaphors serve two main functions beyond mere description or elaboration. Those functions are explanation and evaluation. Explanatory metaphors are concerned primarily with the transfer of knowledge from the target to the source domain. Evaluative metaphors, by contrast, are intended to convey an attitude or mood. Phenomena that call for both explanation and evaluation are especially likely to become a source and/ or target of metaphor. At the core of any emotion is an evaluative judgment. For someone to be angry, frightened, sad, in love, disgusted, proud, and so forth, requires that the situation be evaluated in a certain way - as good or bad, as beneficial or harmful, as just or unjust, as beautiful or ugly, and so forth. Because of this, emotions are a rich source of evaluative metaphors. However, the emotions are also the object of value judgments, and hence the target of evaluative metaphors. Consider, for example, the characterization of emotions as "diseases of the mind." As we shall see, this is one of the major metaphors of emotion, historically speaking. It has an explanatory function (e.g., emotions can disturb orderly thought processes, just as diseases can disturb orderly physiological processes). However, the metaphor is also clearly evaluative. Emotions are "unhealthy." Unfortunately, it is not always easy to distinguish explanatory from evaluative uses of a metaphor. (James Averill, p. 106)