  In the Meditations and Principles, Descartes did not focus on the metaphysical question of how mind and body interact. Rather, he discussed the functional role of mind–body union in the economy of life. As it happens, our sensations serve us well in avoiding harms and pursuing benefits. Pain-sensations warn us of bodily damage. Pleasure leads us to approach things that (usually) are good for us. Our sense perceptions are reliable enough that we can distinguish objects that need distinguishing, and we can navigate as we move about. As Descartes saw it, “God  or nature” set up these relations for our  benefit. They are not perfect. Sometimes our senses present things  differently than they are, and sometimes we make judgments about sensory  things that extend beyond the appropriate use of the senses.