IME a deep conversation's subject actually depends wholly on the individual participants of the conversation. It generally is about a shared topic that is part

IME a deep conversation's subject actually depends wholly on the individual participants of the conversation. It generally is about a shared topic that is part of the self-identification of at least one party (with a non-identifying party being willing to listen to the identifying party in a manner that the identifying party understands to be respectful). For example, between an athiest and a thiest, a deep theological question goes into the thiest's religion with the athiest being at minimum willing to listen in a manner the thiest sees as both participatory (not empty 'uh-huh' responses) and also respectful (no blanket denials or insults). Between two thiests, a deep theological question would go into the nature of their spiritualities, comparing and contrasting, or some specific nuance of a shared thiestic belief. A non-religious deep question can also be positioned on, say, the influence of a specific popular activity. This leads to, for example, heavy and deep debate on the nuances of tennis between two tennis players, or a similarly intimate discussion in which people who suffer from addiction can feel benefit from discussions with other addicts.