undergraduate honorary society, 1776, from initials of Greek philosophia biou kybernētēs "philosophy, guide of life."

Latin phrase, literally "I think, therefore I am;" the starting point of Cartesian philosophy (see Cartesian), from cogito, first person singular present indicative active of cogitare "to think" (see cogitation) + ergo "therefore" (see ergo) + sum, first person singular present indicative of esse "to be" (from PIE root *es- "to be").

"spiritual essence, distinct from matter and supposed in the philosophy of Pythagoras and Plato to be diffused throughout the universe, organizing and acting through the whole of it," 1670s, Medieval Latin, literally "soul of the world;" used by Abelard to render Greek psychē tou kosmou. From fem. of Latin animus "the rational soul; life; the mental powers, intelligence" (see animus) + genitive of mundus "universe, world" (see mundane).

late 14c., from Latin secundum naturam "according to nature" (Augustine, Macrobius, etc.), literally "following nature" (see second (adj.)). A term from medieval Aristotelian philosophy, contrasted to phenomena that were super naturam ("above nature," such as God's grace), extra naturam ("outside nature"), supra naturam ("beyond nature," such as miracles), contra naturam "against nature," etc.