Cogito cogito ergo cogito sum -- "I think that I think, therefore I think that I am;" as close an approach to certainty as any philosopher has yet made.
GNU, n. An animal of South Africa, which in its domesticated state resembles a horse, a buffalo and a stag. In its wild condition it is something like a thunderbolt, an earthquake and a cyclone.
SCRAP-BOOK, n. A book that is commonly edited by a fool. Many persons of some small distinction compile scrap-books containing whatever they happen to read about themselves or employ others to collect.
INFALAPSARIAN, n. One who ventures to believe that Adam need not have sinned unless he had a mind to - in opposition to the Supralapsarians, who hold that that luckless person's fall was decreed from the beginning.