We must never, therefore, let ourselves fall into the way of thinking "ignorabimus" ("We shall never know"), but must have every confidence that the day will dawn when even those processes of life which are still a puzzle today will cease to be inaccessible to us natural scientists.
Nobel Lectures, Chemistry 1901-1921 - Nobel lecture for award received in 1907 - Cell-Free Fermentation (p. 119), Elsevier Publishing Company. Amsterdam, Netherlands. 1966