Abstract: Despite an explosion of interest in the work of Margaret Cavendish in recent decades, her reflections on music have yet to receive much attention among scholars. This paper aims to show that Cavendish advances a wide-ranging and systematic philosophy of music. Its foundation is a theory of musical expression, according to which a work of music expresses an emotion in virtue of resembling it. As Cavendish puts it, 'The notes in musick agree with the motions of passions' (Philosophical and Physical Opinions, 167). On this account, the tempo, volume, and pitch of musical notes resemble such things as the duration, intensity, and valence of the emotions. To give one of Cavendish's examples, 'Slow soft notes, onely on the tenors, are a sad relation' (Opinions, 168). This account of expression is then the basis for accounts of (a) musical harmony, (b) the emotional power of music, (c) musical appreciation, and (d) the benefits of listening to music:

(a) Insofar as the passions the music resembles are harmonious—which for Cavendish is a matter of the extent to which they accord with their natural functions—the music is itself harmonious. As Cavendish uses the term, harmony stands to music as beauty stands to nature. It is in this sense an aesthetic value.

(b) Via the operation of sympathy, music occasions corresponding emotional responses in its listeners. As a result, for Cavendish, 'Musick […] is the greatest Mover of Passion' (Worlds Olio, 113).

(c) According to Cavendish's philosophy of psychology, 'all regular [i.e. harmonious] motion is pleasure, and delight' (Opinions, 15). It follows that, insofar as music is harmonious, it occasions delight in or (what she elsewhere calls) love for music in audiences.

(d) Another commitment of Cavendish's philosophy of psychology is that emotions that are harmonious—in the sense of in according with their natural functions—are healthy. So, again insofar as music is harmonious, it promotes mental health by prompting harmonious emotions in audiences. In Cavendish's words, 'Musick may cure mad folks' (Opinions, 139).

In unpacking these ideas, the paper shows how they relate to themes that play a central role in Cavendish's more familiar views in metaphysics and epistemology— for example, that of the natural order—while anticipating prominent positions in contemporary philosophy of music—for example, concerning musical expression. In closing, the paper situates Cavendish's views in relation to others in the early modern era, specifically, to the humanist tradition and to the views of her contemporaries, Marin Mersenne and René Descartes.