In order to understand what has changed for scientific and scholarly research publication in the transition from the Gutenberg (on-paper) to the Post-Gutenberg (online) era, we first have to make five critical distinctions. If we fail to make any one of these distinctions, it will be impossible to make sense of the unique new possibilities opened up by the online era of ‘Scholarly Skywriting’ (Harnad, 1990) in the ‘Post-Gutenberg Galaxy’ (Harnad, 1991).