All the technical requirements (presses, inks, page-shaped supports, even the art of  negative casting in metal) were then already in place. But there was  as yet no printing because no one was yet aware that by drawing  letters, one was dealing with types. Written signs were taken to be  characters. “Type-identifying” thought had not yet pressed itself  into consciousness. Gutenberg’s great deed was the discovery of  the types inherent in alphanumeric script.
Flusser: Does Writing Have a Future? , p. 48