QUESTION: do wiccan believes, covens or people reject the third gender?
ANSWER: Technically no.
We believe that everyone is born either male or female - though occasionally nature does throw us a loop and deliver a hermaphrodite. However; we are all also made up of a balance of male and female energy. Everone has both and how much you lean either way may vary. You know you have seen many men who are men and like girls but are very feminine in behavior, and girls who are girls who like men that are very strong and male like.
The third gender concept is condidered by most cultures to be a personal choice you can make. It is usually just homosexual or transgender men who live in a culture where this behavior is not well accepted who need something to legitimize their desires. An example of this is India's hijra. They are men who choose to be sexually treated as women.
In American Indian cultures, men with strong female tendencies - the homosexuals - are treated as wise women and trained as shaman. They are offered to important men as second wives.
In most cultures, other than the new world which is weird in so many ways, lesbian bahavior between women is seen as an extracurricular activity and they all often still take husbands and have kids.
Mother Nature has not created more than two genders. The genders are part of natural balance; the yin yang of life. Whether tendencies to want to live outside of these roles is a personal choice or biology gone wrong is still widely debated. It is how you personally decide to deal with it that defines you. Choosing to call yourself third gender, like the hijra, is a choice.
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QUESTION: could a third gender person become a priestess or priest in a coven
While you never know when you are going to meet an asshole who is a bigot, or a racist, or a homophobe, most wiccans and other natural spiritualists are very openminded people when it comes to race, religion, and lifestyle choices.
Any group of people wanting to form a circle group who honor the goddess and the old ways in any of its various forms may decide what kind of people and behavior they want to include. I would point out; however, that excluding people from anything you are involved in is a form of discrimination and generates negative energy. (That's bad...)
A persons choice of sexuality is personal, and for the most part you should not be able to even tell who is gay or straight by watching them walk down the street. I have many gay and lesbian friends and would gladly worship with them. In all honesty, the flamingly gay people irritate me a little. Sex and sexuality is something that should be held in some modesty no matter what your choice is, just to respect others.
If you want a gay, lesbian, or transgender person to lead your coven, make that choice because you respect their wisdom, trust their guidance, and believe they are worthy of the position. Not because they're gay.
And remember that no matter who you choose as leader - all initiated members are considered priests or priestesses, and the group should be a democratic membership and work together.