One of the most important things about a circle or society for people working on a topic is that it keeps its members honest/careful, using an expectation of criticism for statements that violate the scientific/philosophical/other norms of the community to keep people cautious.
A good scientist or philosopher or historian or practitioner of many other disciplines should welcome well-founded criticism, not be shy of levelling it at even those that share their values, and be prepared for lively discussion in groups for their topics.
This is why academia works. This is why circles of philosophy work, and this is why whenever any community insulates itself from criticism it so quickly rots. Good work *can* come from the lone thinker, but it's rare that a lone thinker can manage that for any length of time.