“I incline to Cain’s heresy…I let my brother go to the devil in his own way.” 

Utterson describes his attitude of tolerance toward others’ misdeeds. The quote proves ironic since Utterson will act in the opposite way with regard to Jekyll, showing great concern for his moral and physical downfall. 

“You start a question, and it’s like starting a stone.”

Enfield explains why he declines to get involved in Hyde’s case. Once you ask a question, it becomes like a stone rolling down a hill; he does not want to be judgmental or ruin people’s reputations. This quote, too, is ironic since both he and Utterson will become involved in the case of Jekyll and Hyde. 

“But it is more than ten years since Henry Jekyll became too fanciful for me.”

Dr. Lanyon broke his friendship with Jekyll because the latter became involved with outré scientific theories. This professional and intellectual conflict between the two men becomes a central motivating force for Jekyll.