Is this where I am supposed to say 'learn to abc'? I'm not sure if people are being deliberately obtuse or if everyone just reads these rank titles and assume they are nonsense words.
Wikipedia wrote:
In parts of Europe, as in later medieval Germany, spending time as a wandering journeyman (Wandergeselle), moving from one town to another to gain experience of different workshops, was an important part of the training of an aspirant master. Carpenters in Germany have retained the tradition of traveling journeymen even today, although only a few still practice it. In France, wandering journeymen were known as compagnons.
Or in other words, your apprenticeship is finished. Your teacher is no longer responsible for your training. Learning from experience is more effective than learning by rote. You are expected to go out into the world and learn from your experiences instead of blindly relying on the words of others. It's your own responsibility to make it to take your craft to the next level. For your mentor to teach you further would be a disservice because you will never be treated as a master if you have not developed your own style and technique.
Use some of these rationales the next time you are asked to explain why you can not teach higher level skills.
And that's the IC rationale which dovetails perfectly with the gameplay rationale -- the mentor system is for helping newbies get accustomed to the game. It is not a replacement for exploring the environment in order to build up your character.