How did Jean-Jacques Rousseau influence the theory of art as emotional expression?

Jean-Jacques Rousseau was a pivotal figure in the development of 18th-century aesthetics, specifically regarding the shift toward viewing art as a medium for emotional expression rather than mere imitation.1

In his essay concerning the origin of languages, Rousseau proposed that the arts—particularly music—function as forms of emotional expression. This theory challenged the prevailing view of art as mimesis (imitation of nature), which had been a dominant principle since antiquity. By prioritizing the capacity for feeling and spontaneity over rational theory, Rousseau argued that art should reflect the internal state of the individual.12

His influence on this transition was profound:
* Shift in Focus: He helped move aesthetic discourse away from the "false glitter" of society and toward the authentic expression of human sentiment, pity, and benevolence.2
* Musical Theory: His ideas provided a compelling explanation for the power of music, leading many late 18th-century thinkers to reject the notion that music must be representational in favor of it being an expressive art form.1
* Romantic Legacy: By championing introspection and the importance of the individual's conscience and feelings, Rousseau laid the groundwork for the Romantic movement, where imagination and emotional expression became the defining features of artistic insight.21