  Matters are different for the errors of sensory representation. The senses depend on media and sense organs and on nerves that must run from the exterior of the body into the brain. God sets up the mind–body relation so that our sensations are good guides for most circumstances. But the media may be poor (the light may not be good), circumstances may be unusual (as with the partially submerged stick that appears as if bent), or the nerves may be damaged (as with the amputee). In these cases, the reports of the senses are suboptimal. Since God has set up the system of mind–body union,  shouldn't God  be held accountable for the fact that the senses can misrepresent how things are? Here Descartes does not appeal to our freedom not  to attend to the senses, for in fact we must often use the senses in suboptimal cognitive circumstances when navigating through life. Rather, he points out that God was working with the finite mechanisms of the human body (7:88), and he suggests that God did the best that could be done given the type of parts needed to constitute such a machine (extended parts that might break or be perturbated in an unusual manner).