"Margaret Cavendish (1623--1673) is a fascinating figure who is getting increasing attention by historians of philosophy these days, and for good reason. . . . She's an interesting advocate of a vitalist tradition emphasizing the inherent activity of matter, as well as its inherent perceptive faculties. She's also the perfect character to open students (and their teachers) up to a different seventeenth century, and a different cast of philosophical characters. This is an ideal book to use in the classroom . The Philosophical Letters (1664) gives us Cavendish's view of what was interesting and important in the philosophical world at that moment, a view of philosophy as it was at the time by an engaged participant. There are few documents like it in the history of philosophy . Deborah Boyle's Introduction provides a very accessible summary of Cavendish's natural philosophy, as well as good introductions to the other figures that Cavendish discusses in the book. Boyle's annotations are not extensive, but they are a great help in guiding the student toward an informed reading of the texts." --Daniel Garber, Princeton University