• 1 · Religion and Magic
• 2 · Nature
• 3 · Human Being, Man in General
• 4 · Society, Civilization, Culture
• 5 · Abstract Ideas and Concepts
• 6 · History
• 7 · Bible
• 8 · Literature
• 9 · Classical Mythology and Ancient History

• Top
• 5 · Abstract Ideas and Concepts
• 51 · Generalities
• 51G · Some Characteristics of Matter
• 51G4 · Hardness

51G4(+3) · Hardness (+ symbolical representation of concept)