Polarity is a much-debated concept in contemporary Paganism. It is conventionally held to be the interaction of the masculine and feminine principles in the universe. This is problematic if these principles are directly mapped onto men and women.
The first polarity we experience in life is probably self and other, as we separate ourselves from the dyad of mother and baby. Whilst this is received wisdom among child psychologists and has been used to justify all sorts of essentialist nonsense about the role of the mother in the development of the child, it does seem to make some sort of sense.
In order for gnosis / samadhi / transcendence to occur, the Other must become the Beloved Other. Tat tvam asi.
For Christians, the Beloved Other is probably Christ; for Jews, it is the Godhead (maybe even the Shekhinah?); for Sufis, perhaps Khidr; for Muslims, presumably Allah; for Hindus, the Universe; and for Pagans, it is the Universe, Nature, or a specific deity.
The other is initially that which is not-Self. It is this projection which gives rise to the Shadow, as we reject those parts of ourselves that we cannot integrate into the Persona. Interestingly, Jung also came up with the idea of the Bright Shadow to describe the part of the Shadow that is not rejected, just different. Jungians generally refer to this as the Anima or Animus and assign it the opposite gender to the Persona. But it doesn't have to be the opposite gender to the Persona.
The Other appears again and again in mythology as the Dark Twin. Sometimes it is the Bright Shadow - the Beloved Other; sometimes it is the Dark Shadow - the rejected aspect of the self.
Also there are other aspects of the psyche in Jungian thought - the inner child, the inner wise person; and again, these could be either gender or none.
Alternate Currents: Revisioning Polarity Or, what's a nice dyke like you doing in a polarity-based tradition like this? by Lynna Landstreet