"Concept is a vague concept."

Ludwig Wittgenstein (1889–1951)

"Tell people there's an invisible man in the sky who created the universe, and the vast majority will believe you. Tell them the paint is wet, and they have to touch it to be sure."

George Carlin (1937–2008)

"Logic will get you from A to B. Imagination will take you everywhere."

Albert Einstein (1879–1955)