Publication of *Philosophical Letters*, furthering her metaphysical theories.
Margaret Cavendish's Philosophical Letters was published on January 1, 1664, to engage critically with the works of renowned philosophers of the time. Through this book, she further developed her metaphysical ideas, challenging existing views and discussing topics like materialism and the nature of existence. Her letters demonstrated her courage in refuting well-known male philosophers, asserting her space within the philosophical community.