I think we can all agree that our body is a reckless thing, always wanting its desires satisfied quickly and completely. So any choice we make which denies what our body wants speaks loudly about the presence of some other motivating force in our nature. For instance our will—this determination coming from within which sometimes drives us to make decisions either for our own good or the good of others in spite of the instant gratification our physical body may be demanding. Or how about those deeply seated emotions in our being which often prevent us from a reasonable response as we interact with the world around us? And above all, what about our conscience, this inherent sense of right and wrong that so mightily contributes to the control and direction of our behavior?
All people, in varying degrees, share attributes and capabilities that come from a deeper component of our being—the immaterial part of the nature of man.
Now since the mind is accessed both by the physical body and our immaterial nature, it can clearly be seen as the critical link between the two. I think of the mind as a gateway which facilitates change going either direction. Bad behavior in the body sickens the soul, and an unhealthy soul fosters a further deterioration of our behavior. But the opposite is also true: a vigorous soul serves to strengthen the resolve of the mind, which in turn promotes better behavior. And better behavior then further bolsters the health of the soul.
Excerpted from: Free from the Power of Sin: The Keys to Growing in God in Spite of Yourself