1. Contemporaneity: Both lived in one period; this alone does not document an encounter.
2. Feasible meeting: Their dates and circumstances make meeting realistically possible.
3. Established meeting or hearing: Reliable evidence shows at least one encounter or some hearing, although the particular report may still use ʿan.
4. Established disconnection: Evidence shows the required encounter or hearing did not occur or could not occur.
The dispute concerns the threshold between cases 2 and 3 for a reliable non-mudallis. Case 4 cannot be repaired by the mere presence of ʿan.