Throughout time, many of the prophets were able to heal people of their illnesses. But what was the purpose in the ability to heal the sick? Was this a way of telling people that they represented God? Or did these prophets understand the causes of these illnesses?  

If we are to understand the source of our illness, or disease, will we be able to cure our own infliction?  Do all people have the capability to heal?  In the Ofudesaki and the Osashizu are the following:

However serious an illness will become, I never say that it will not be cured. 12-52 Ofudesaki

The saving of those whom doctors are unable to save is the foundation of the path. You tell them the teachings (about the soul). They listen and they are healed.Oct 17, 1893 Osashizu

Understanding the soul/heart is important in the removal of an illness. It helps you understand how causality and karma work.