حكمه: لا ينال المراد منه إلا بالطلب، ثم التأمل في معناه.
Its intended sense is reached only through inquiry and then reflection on its meaning.
The sequencing signaled by thumma matters. First gather evidence about usage, language and context; only then weigh that information to identify the intended meaning. Unsupported preference is not enough.
In khafi the emphasis lay on investigating a particular instance. Mushkal requires, in addition, a structured examination of alternative understandings of the expression.