Elisabeth was not satisfied with this answer, so she wrote to Descartes again. In this letter, dated June 20, 1643, Elisabeth writes that she cannot "understand the idea through which we must judge how the soul (nonextended and immaterial) is able to move the body, that is, by that idea through which you have at another time understood heaviness ... And I admit that it would be easier for me to concede matter and extension to the mind than it would be for me to concede the capacity to move a body and be moved by one to an immaterial thing." Jaegwon Kim cites this as the first causal argument for the doctrine of physicalism in philosophy of mind. In another letter from Elisabeth to Descartes dated July 1, 1643, Elisabeth agrees with Descartes that our senses are evidence that the soul does move the body and the body moves the soul, but that this interaction does not teach us anything about how this happens. In Elisabeth's correspondence with Descartes, we can see that Elisabeth assumes that Descartes does have an account of how the soul and body interact and asks for clarification on how the soul does this. In fact, Descartes did not have an exact account of how this happens, but merely assumed the soul had this capability. This particular correspondence between Descartes and Elisabeth ended with this July 1 letter.