Answer:
A lawyer working for a large corporation.
Step-by-step explanation:
Mr. Utterson is described as a lawyer in the text, and it's suggested that he has an approved tolerance for others and a catholicity of good-nature. He inclines to Cain's heresy, meaning he lets others go their own way even if they're going down a negative path. He is undemonstrative at best and has a bond with Mr. Richard Enfield, who is also a man about town.
Based on these descriptions, it can be inferred that Mr. Utterson is likely a lawyer who values understanding and tolerance in his dealings with others. Thus, it's most likely that a lawyer working for a large corporation would share Mr. Utterson's point of view about humanity.
It's possible that a social worker in a large city might also share his views, but they would likely have a more hands-on approach to helping those in need. A teacher in an exclusive private school may have different values and priorities, and a police officer in a small rural community may have a more strict and enforcement-focused perspective on justice and human behavior.