A good and detailed introduction to some key Knowledge organisation concepts and a few handy links by a learned chemist (interesting how so many “classifiers” are chemists!). I’m not sure I agree with the distinction between the role of the encylopedist and the information professional (having been both) – it seems to me that there is a lot of overlap! I am also not convinced that it is useful to talk about notions of only being able to categorise a topic successfully once it has ceased to grow. That seems to be calling upon a Platonic ideal where all that can ever be known is known. It seems to drive you down the same philosophical hole of deciding that you can’t prove or know anything anyway. In the real world, the notion of “successful” isn’t a Platonic ideal. A categorisation can be both successful and require updating. There are hardly any real world examples of a topic that has ceased to grow, except maybe very specific practical contexts, e.g. a service company that generated no physical products and has gone out of business (until the social historians start studying it). I find it hard to think of any truly “dead” topic in an abstract sense (alchemy? ancient Aramaic? – but people do still study them).