> No doubt true, but there are alternatives which Java has not pursued – for example, support multiple versions of a class, code is JITted to work with the late

> No doubt true, but there are alternatives which Java has not pursued – for example, support multiple versions of a class, code is JITted to work with the latest version at JIT time, but other versions are detected and cause a fallback to interpreter mode This is already how it works. You can define any method definition at runtime and the JIT will fallback until it can optmise the new version again. What Java doesn't allow is modifying classes or interfaces because that would compromise the type safety of the language, which AFAIK is not a concern in Smalltalk.