What do the townspeople believe is the cause of Dimmesdale's poor health in The Scarlet Letter?
It is in Chapter 9 that Arthur Dimmesdale's failing health is first referenced, and the views of the townspeople concerning what is behind this physical waning. The narrator makes clear that the townspeople think in general that is failing physical health is the result of his zealous approach to his work and his neverending labours to remain as holy and as pure as he can:
By those best acquainted with his habits, the paleness of the young minister's cheek was accounted for by his too earnest devotion to study, his scrupulous fulfilment of parochial duty, and, more than all, by the fasts and vigils of which he made a frequent practice, in order to keep the grossness of this earthly state from clogging and obscuring his spiritual lamp.
The majority of townspeople therefore believe that what lies behind Dimmesdale is his own unceasing labours as their priest, and that he is so committed to godly acts and study that he is not looking after himself as he should. In particular, their view that his frequent fastings and night time vigils are to prevent his "spiritual lamp" from being "clogged and obscured" are cited as a reason why he is becoming so emaciated and pale. Chapter 9 makes it clear that the townspeople were so concerned about Dimmesdale's health that they felt his death might be imminent, which of course lies behind the suggestion that the new doctor, Chillingworth, be placed in the same house as Dimmesdale so that he could look after him in his poor condition.