What is a word for a person who has been initiated into secret knowledge (apprentice, ___, master)?
Solution 1:
Journeyman would feel like the most natural choice to me.
(Addendum: Freemasonry goes with fellow craft between entered apprentice and master mason, but that's a bit wordy for my tastes.)
Solution 2:
It sounds like adept may meet your needs. The Hermetic Order of the Golden Dawn initiatory structure has 10 grades divided into three tiers, and the middle tier is the adept grades (5=6 adeptus minor, 6=5 adeptus major, and 7=4 adeptus exemptus).
Honestly, I would also be perfectly comfortable using initiate for your situation, not really feeling it very strongly has the beginner implications you mention. Adept clearly has a much stronger connotation of competence, though.
If you were to go with this option for your middle grade, I would also suggest thinking about using initiate or neophyte rather than apprentice for your initial grade, to distance a bit further from the traditional guild apprentice-journeyman-master structure. In fact, drawing a bit further from the Golden Dawn, in which the next grade up from the adept tier is 8=3 magister templi ("Master of the Temple"), we could get a super-sexy progression of neophyte-adept-magister.
Solution 3:
Whenever I hear secret knowledge, naturally I immediately think of Freemasonry.
So, I understand there are three degrees of Craft or Blue Lodge Freemasonry (info via Wikipedia):
- Entered Apprentice – the degree of an Initiate, which makes one a Freemason;
- Fellow Craft – an intermediate degree, involved with learning;
- Master Mason
Therefore, fellow seems appropriate here. You may simply go with member.
Another word that may fit is journeyman. Might have problems with gender neutrality on that one, though.
Solution 4:
Just for fun, I'll throw in another word, based on the question's tag line more than on the content: Acolyte