 Proponents of this interpretation are apt to cite Third Meditation passage distinguishing what’s revealed by the natural light, and what’s taught by nature (see  Section 4.3).  In order to extend perfect knowledge beyond the privileged class of truths (revealed by the natural light), it is necessary to establish the general veracity of the C&amp;D Rule. Thus, the need (on this interpretation) for Arc 2 in the broader project.