Notwithstanding the fact that the Buddha essence is non-polar, Buddhist iconographers use sexual polarity to symbolize the twin concepts of insight and compassion.
All goddesses are symbols of insight and the gods represent compassion.
The union of compassion and insight symbolizes the non-polarized state of bodhicitta, or the mind of enlightenment, which is represented visually by showing two deities engaged in sexual union. This sexual metaphor is also used to denote the highest stage of yoga in which there is no polarity, no discrimination, and the truth is indivisible as the vajra itself. It may be added parenthetically that while such images, whether statues or paintings, are today much sought after by collectors and boldly displayed in museums, in Tibet they were always meant to be seen only by the initiated. The rites associated with these images were also arcane and not for public consumption. The couples of Buddhist iconography celebrate this deep harmony of the sexes.