I just finished my capstone paper for the Proverbs class focused on the heart.  It was an amazing study.  I had no idea how much the Bible speaks to the heart as the core of our full inner being.  Even though postmoderns might claim that the writers of Scripture actually were referring to the upper cortex or higher brain functions when they talked about the heart, I may disagree to some extent.  Yes, the higher brain functions to form beliefs, values, etc. but, its more than an academic construct.  There is feeling, passion and emotion with our faith and that must come from more than our logical side.  It is no wonder that the Sages teach the young to 'guard diligently' the heart for from it comes all the issues of life.