• Salāyatana Vibhanga Sutta

A series of definitions of the

• six internal senses,
• six external sense objects,
• six groups of consciousness,
• six groups of contacts,
• eighteen mental researches,
• thirty six tracks for creatures,
• six satisfactions to the banished,
• three bases of mindfulness, and
• the supreme trainer of the human heart. M.iii.215-22.