Quote from ACIM Text Chapter 2, Section 5 - The Function of the Miracle Worker.

It should be emphasized again that the body does not learn any more than it creates. As a learning device it merely follows the learner, but if it is falsely endowed with self-initiative, it becomes a serious obstruction to the very learning it should facilitate. Only the mind is capable of illumination. Spirit is already illuminated and the body in itself is too dense. The mind, however, can bring its illumination to the body by recognizing that it is not the learner, and is therefore un-amenable to learning. The body is, however, easily brought into alignment with a mind that has learned to look beyond it toward the light.