  In both Logic, Rhetoric and the Fine Arts and Fine Arts, Reid shows a commitment to the importance of emotion and of expression in understanding art and artworks. He writes, “Expression is the capital thing in all Compositions of Music” (Logic, Rhetoric and the Fine Arts 288) but textual evidence for an expression theory in those works is equivocal compared with Reid's remarks in EIP and in his correspondence. In lecture notes Reid appears partially to endorse expression theory and partially to endorse emotional arousal theory. Emotional arousal theories of art are closely related to expression theories since both appeal to emotion as an essential feature of an artwork's aesthetic quality, but they differ on a crucial point. Emotional arousal theories explain the aesthetic quality of an artwork in terms of the way an artwork causes the expression or experience of emotion in the viewer or listener, and not (as on expression theory) in terms of the way in which an artwork's aesthetic qualities are caused by the artist's representation of his or her emotion in qualities of the artwork. In Reid's discussion in Lectures on the Fine Arts he appears to combine both theories to suggest that the emotion expressed by the artist must also be the same emotion aroused in the viewer or listener. The playwright introduces “a sign or expression of the passions, &amp; when this is accomplished, it affects us and causes the same passion in us...” (Lectures on the Fine Arts 51). In his mature, published work, advocacy of the emotional arousal theory diminishes.