Can you discover the periodic table?

By Brian Clegg

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 classification system that goes from O to B, A, F, G, K, and M. This system is not part of the reality that is Betelgeuse, it is a classification system that people devised – it’s a representation of something – a different class of thing to a star. As such, the classification system cannot be discovered: it has to be invented or created by human beings.

If I am a non-realist, who presumably doesn’t thing there is a defined reality behind the label Betelgeuse, this has no effect on the constructed classification system, which is still invented or created.

Let’s now shift that picture to Mendelev and the periodic table. As a realist I can accept that there are relationships between different atoms based on their atomic weights and properties – that is something that can be discovered. But like the stellar classification system, I would suggest that a periodic table is a representation, a model, not an aspect of reality. As such, even as a realist, I would suggest it can only be created or devised, not discovered.

* Note this is my interpretation of these terms – not everyone will necessarily agree

Now Appearing is the blog of science writer Brian Clegg (www.brianclegg.net), author of Inflight Science, Before the Big Bang and The God Effect.