In the field of medicine, if you're sick you need a doctor. A doctor has already studied how to deal with your ailments, and human beings are imperfect. There any many ailments of the psyche and the soul that need to be treated, and the serious murshid, or spiritual master, is also really a doctor of the soul: a person who can heal the wounds of the soul in the same way as a medical doctor takes care of our physical problems.