Paul E. Griffiths argues that most research on the emotions has been as
misguided as Aristotelian efforts to study "superlunary objects" -
objects outside the moon's orbit. Such subjects exist, of course, but
studying them as a group produces no useful results because they share
no traits other than an arbitrarily defined location. Similarly,
Griffiths show that "emotion," as currently defined, groups together
psychological states of very different, and thus not comparable, kinds.
According to Griffiths, theoretical research on emotions took a wrong
turn by not fully exploring the relevant empirical evidence. Griffiths
provides a detailed overview of this material, drawing on ethology,
evolutionary biology, neuroscience, cognitive psychology, and
anthropology of the emotions. He identifies and assesses the relative
merits of three main theoretical approaches - affect program theory,
evolutionary psychology, and social constructionism.