During the first half of the 19th century, a variety of reform movements emerged in response to social, political, and economic changes in the United States. These movements sought to address issues such as abolition, women's rights, and education reform. One prominent figure associated with these reform movements was a well-known transcendentalist who emphasized individualism and self-reliance, advocating for moral improvement and social reform. Who is this figure, renowned for their philosophical contributions to American reform, especially in the realms of education and social responsibility, and whose writing encapsulated the spirit of the era?