Written ideas
An Italian manuscript containing 27 of Cicero's speeches. Genève, Bibliothèque de Genève, Ms. lat. 101
An idea may reach another person or groups orally. But while it is may be airborne, its scope is pretty limited. A speech may infect an audience, a harangue may embolden an army, a sermon may excite a congregation, but fertilisation happens there and th…