I follow the excellent historian and philosopher of chemistry Eric Scerri on Facebook and a recent post of his intrigued me. In it, Eric uses the verb 'discovered' for what Mendeleev did with periodic table. When I queried this, he suggested that the use of the term depended on whether or not you are a realist. But I'm not sure if that's true. Let's take a simpler example, then come back to the periodic table. Specifically, we'll use the star Betelgeuse, the distinctly red one of the four main stars of Orion. If I'm a realist*, then I think there is something real out there that I am labelling Betelgeuse. In good Kantian fashion, I can't know the reality - the 'Ding and sich' - but I can report on the sensory data from Betelgeuse and believe that I am talking about something that really exists. As it exists independent of humanity, we can discover it. However, Betelgeuse is also a class M star on the endearingly random looking stellar cl...