  Le Grand described the mind-body union in terms directly borrowed from Descartes. However, Le Grand attempted to explicate further than did Descartes the nature of the mind-body union. According to Le Grand, there are three kinds of union, each possessing its own principle which effects that union: the first is that of two minds whose principle of union is love; the second is that of two physical bodies whose principle of union is local presence; and the third is that of the mind and body whose principle of union is actual dependence. Just as two physical bodies are joined by physical contact, and as two minds are joined by love, the mind and body are joined by a mutually dependent activity. So long as the body actually receives  its specific motions dependently on the soul, and the soul actually receives its local motions (passions) dependently on the body, the spirit and the body are joined. Although there can be no mode common to mind and matter, there is this mutual action. While there is no mode shared by two different substances, there is a similitude and relation that exists between mind and body: “This similitude and relation we have formerly affirmed to consist in action and passion” (1694, p. 325). In other words, just as the body is capable of receiving and transmitting local motions since motion is a mode of matter, the mind is capable of varying passions since passions are a mode of the mind. It is by the mutual commerce of such motions and passions that the mind and body are said to be united. The mutual activity said to occur between the mind and the body is a property which follows only from the union of mind and body and cannot proceed from either alone, “And the truth is, since neither body can think, nor mind be capable of dimension, there can be no mode common to mind and body, except a mutual acting of each upon each, from which alone the properties of both can follow” (1694, p. 325).