Determining mutual familiarity with a topic or subject depends on the context in which the question is asked. If this pertains to shared knowledge about a specific subject, here are some steps involved in assessing whether both parties are familiar with it:
Contextual Clues: Before asking, consider if there have been previous conversations or experiences where the subject was discussed or encountered together. This can provide initial insight into the other person’s familiarity.
Direct Inquiry or Discussion: Engage in conversation about the subject to see if both parties respond with understanding or information. This can reveal the level of familiarity and understanding each has.
Observational Cues: Look for verbal and non-verbal cues that indicate recognition or unfamiliarity, such as nodding in agreement, asking clarifying questions, or providing insights about the subject.
Pre-existing Knowledge: Consider whether the subject is commonly known or specialized. For example, topics of general knowledge like basic science or historical events may have a higher chance of mutual understanding compared to niche or technical subjects.
Cross-checking Information: Sometimes, confirming the other person’s understanding by asking them to explain their perspective can help in verifying mutual familiarity and identify gaps in knowledge.

Ultimately, discovering mutual knowledge can strengthen communication and ensure that discussions are productive and enlightening.