التخصيص قد يكون بمخصص مجهول
Specification may occur through an initially indeterminate specifying factor.
In another case the specifying evidence and the excluded cases are already identified; this is known specification.
With a known specification, one can identify the cases excluded. With an initially indeterminate specification, one knows that an exception exists but may need further explanation to identify its full boundaries. The source supplies examples of both situations.