Neleus, family (owners of Aristotle's library), 175
Nicomachus, father of Aristotle, 172
Notions, Epicurus' view of, 215
Number, original of things, 24; relation of ideas to, 167
Obedience, through disobedience, 122
Obscure, epithet of Heraclitus, 15
Odd, v. Even, 24
Opinion, v. Knowledge, 33, 35
Oracle, answer of, respecting Socrates, 107; maxim engraved on, 113
Organism, idea of, in Aristotle, 185, 205