I would like to second this one!

If you want to have beginners mode, I think you need to include run-time aspects as well as Ben mentions. It should be possible to put the general doesNotUnderstand in a beginners mode, which checks for these cases

- messages send to nil, explaining what is the likely cause(s).��

- the case mentioned by Ben

- check if the message is understood by the class or object (several have mentioned the class/object side issue).

- check which classes implements the method which was sent, and perhaps even suggest to open the implementers browser

Good luck with the project!

Best,

Kasper