Why cannot women become buddhas?
Buddhist academics explain that in the formation of the Tripitaka some parts are older than the others. The oldest is the Patimokkha, which is the monastic code for both monks and nuns. In Theravada there are 227 rules for monks and 311 for bhikkhunis.
We found that the part of the Tripitaka where were the passage referring to women's inability to become buddhas happened at least 500 years after the Buddha's passing away when Mahayana already had come into existence. At that time there already developed the ideal that the Buddha was not ordinary being but had a supernatural existence. Buddhists began to prescribe to the Buddha the 32 Mahapurisa characteristics as believed to be the qualities of great monarch. One of these characteristics prescribed that the Buddha must have his penis in a sheath that is covered, meaning that the Buddha has transcended sexual desire. Later on this requirement is emphasised only 'having the penis,' hence ending up with the understanding that women cannot become buddhas. This belief continued on for a thousand years. Teachers in the later time had difficulty explaining this limitation on gender and developed the teachings to accommodate women by saying that if a woman achieved a higher standard of spiritual development she may be transformed into a male.
Some of the Mahayana Sutras e.g. Sukhavati Vyuha Sutra mentions Amitabha Buddha who presides over the Western Paradise. Within this realm (Buddhaksetra), women who have strong faith in him will be born as men. Such belief is based, not on the dislike of women, or that women cannot practise dharma, but out of compassion that women have to go through the physical suffering of child birth, etc. This is true as in the olden days medical care was far behind. Hence sometimes we hear a comparison between a woman having to go through child birth to a man going to war. With this understanding and out of compassion, Amitabha Buddha allows women with faith in him to be born in his realm as men.
Another sutra not much known among the Thais is that of Aksobhaya Buddha who presides over in the Eastern Paradise. This realm is different from that of Amitabha Buddha, a woman born in this realm retains her womanhood, and should she desire to have a child, a child is born without conception, without having to go through the suffering of child birth, etc, and eliminates completely the involvement of the male counterpart. This may be seen as compassion expressed by Aksobtaya Buddha, one step more advanced than Sukhavati in the sense that it recognises womanhood and motherhood.
Again the Saddharmapundarika Sutra, a major text for Mahayana of all schools, mentions in one of its chapters, a daughter of a naga (divine serpent) who was as young as 8 years old but well versed in dharma. She offered a jewel to Sariputra. As Sariputra received the offering she stated that she can change into male form faster than the time Sariputra received the offering from her. In this context, this particular message means that one becomes enlightened, then transforms the gender. In other words one has to transcend gender in order to be enlightened. To be enlightened is to be free from all bindings and limitations including gender. Once enlightened, male or female retains no difference.
Another important Mahayana Sutra, the Vimalakirti Nidesa Sutra, mentions an encounter between Sariputra and a goddess who resides in Vimalakirti's residence. After having a long dharma talk with her, he was impressed at her knowledge of dharma in spite of the fact that she was only a female. As if realizing higher level of dharma belongs only to male, he asked her why she still retains female gender. The goddess replied that since she had been there for 12 years, she had examined her mind and was not able to hold on to anything female. As this was the case, she was not able to change her gender. While discussing, with her miraculous power, she transformed herself into Sariputra and vice versa. The goddess who was now in Sariputra's form asked Sariputra who was now in the goddess' form if he could change back to his own form. Sariputra said that having examined himself (which was then herself) he could not find the essence of being female. The goddess again reversed her miraculous power and returned Sariputra to his former self, and she to her former self. Then she explained that in the practice of highest dharma there is no essence of being male or female. Thus how can one hold on to being male or female? In the practice of dharma one should not hold on to any particular form, neither male nor female. An enlightened mind is beyond clinging e.g. clinging to male or female, good or bad. Lokuttara dharma is non-duality; enlightenment is a state of mind which is free from the realm of the conventional.