The Elements of Euclid - Part 1 In Book 1 of the Elements, following the Five Postulates, Euclid states five Common Notions, or Κοιναὶ ἔννοιαι [Koinai ennoiai] (Fitzpatrick 7): GreekEnglish αʹ. Τὰ τῷ αὐτῷ