Palindrome (; "again") and ' (; "way, direction"). Palindromes date back at least to 79 AD, as a palindrome was found as a graffito at Herculaneum, a city buried by ash in that year. This palindrome, called the Sator Square, consists of a sentence written in Latin: "Sator Arepo Tenet Opera Rotas" ("The sower Arepo holds with effort the wheels"). It is remarkable for the fact that the first letters of each word form the first word, the second letters form the second word, and so forth. Hence, it can be arranged into a word square that reads in four different
Principle of plenitude Principle of plenitude The principle of plenitude asserts that the universe contains all possible forms of existence. The historian of ideas Arthur Lovejoy was the first to trace the history of this philosophically important principle explicitly. Lovejoy distinguishes two versions of the principle: a static version, in which the universe displays a constant fullness and diversity, and a temporalized version, in which fullness and diversity gradually increase over time. Lovejoy traces the principle of plenitude to the writings of Plato, finding in the "Timaeus" an insistence on "the necessarily complete translation of all the ideal possibilities into actuality". By contrast,