Do what thou wilt shall be the whole of the law.
As my fellow illuminists know, magickal names are generally written in Latin, and Latin gives no room for gender fluidity (i.e. Frater Lux, Soror Caeli). I've seen a few posts in other forums about how being transgender may or may not fit in with this binary system.
Well, I feel there is answer to this:
It really has nothing to do with your personal identity. You could identify as agender, androgyne, or neutrois, and you will never fall out of place in the temple. The use of Male and Female pronouns has to do with the balance of their energies, masculine and feminine. Whichever one may identify with strongest could be the prefix you choose. If you identify with both equally, or neither, then choose one for the particular energy you may wish to portray in the ritual whether there are other participants or in solitary. You don't have to identify personally as a Frater or Soror. In magick you essentially must transcend gender as well as reconcile them on the spiritual level.
"The soul is beyond Male and Female as it is beyond Life and Death." — Aleister Crowley
Eliphas Levi's Baphomet is the symbol of this union. It is the "Great Androgyne" of occultism. In occult spirituality and philosophy it doesn't matter what your physical sex is; it's all about the symbolic.
"Every man and every woman is a star." — Aleister Crowley
This can say two things: we are all on our own individual orbit or path in the universe, and stars are simply points of light with no gender assignment, so everything is open to possibility. Planets are, of course, physically without gender, but in astrology they do have masculine and feminine associations.
So, despite the binary polarity of the universe, the soul is ambiguous. You have to let go of personal identity when doing magickal work, because beyond this flesh we are male, female, both and neither. Besides, Thelema is a philosophy (and religion) of tolerance, save of intolerance.
Love is the law; love under Will.