What theory about Dimmesdale's disease and its cure is expressed in chapter 9 of The Scarlet Letter?
Page. 120 paragraph beginning "thus roger chillingworth scrutinized his patient carefull...."
Chillingworth believed it was essential to know Dimmesdale well before he could cure him. He needed to know about his mind and heart, not just his physical body. The text says that for Dimmesdale "thought and imagination were so active...that the bodily infirmity would be likely to have its groundwork there." In other words, Chillingworth doesn't believe that Dimmesdale's disease is physical. The cure then, in Chillingworth's mind, was to find out Dimmesdale's secret. Once the secret was out, then Dimmesdale might be healed.