Recent commentators have raised methodological questions about how women philosophers of the past can be incorporated into the philosophical canon. One common and useful method of inclusion is to show that these women participated in the great intellectual debates of their time, and that they were perceptive critics of their famous male contemporaries. This is the usual approach taken to the philosophical writings of Princess Elisabeth of Bohemia, the friend and correspondent of René Descartes. On the basis of her famous exchange of letters with Descartes (from 1643 to 1649), Elisabeth is celebrated as one of the first writers to raise the problem of mind–body interaction for Cartesian dualism. She is also remembered as the intellectual inspiration behind Descartes' final treatise, The Passions of the Soul (1649), a work that developed out of their correspondence. In the preface to another text, Descartes commends Elisabeth for ‘the outstanding and incomparable sharpness’ of her intellect. He describes her as ‘the only person I have so far found who has completely understood all my previously published works’. Today she is one of the best-known early modern women philosophers – despite the fact that she left no systematic philosophical writings of her own, and that her key philosophical contributions are in the form of letters. Other than her correspondence with Descartes, there are only a handful of letters from Elisabeth to other male thinkers, such as Nicolas Malebranche, Gottfried Wilhelm Leibniz, and the Quaker Robert Barclay (1648–90).