The discussion centers on al- for prior reference (العهد), generic essence (الحقيقة), and exhaustive inclusion (الاستغراق). Prior reference selects something identifiable; generic essence concerns a nature; exhaustive inclusion ranges over members of the class.
UseReferenceMain clue
Prior reference (العهد)A known referentMention, context, mental familiarity
Generic essence (الحقيقة)The nature of a kindClass description, not counting members
Exhaustive inclusion (الاستغراق)Every relevant memberEvidence of comprehensiveness or exception
The form «الرَّجُلُ» cannot be assigned one of these readings merely from its article; sentence-level and discourse-level cues matter.