(Abstract for the 2019 conference of the Sophia Centre of Cultural Astronomy, UK, about "Light and Dark", about the philosophy of the Yijing; it was rejected.)
In New Age circles and modern culture generally, it is routinely claimed that the Chinese twin principles Yin (cloudy mountain slope, shadow) and Yang (sunny mountain slope, brightness) are equal. This is contrasted with and deemed superior to "Western" dichotomies such as good vs. evil. The equality is deemed crucial when these two principles pertain to the sexes (Yin feminine, Yang masculine) but, eventhough gender equality may be desirable, it does not follow from the Yin/Yang symbolism. Equality is a product of culture, it is artificial (like other desirables: justice, marriage) and is hard to find in the state of nature; whereas Yin and Yang are descriptors of all processes in nature.
The Yin/Yang classic par excellence, the Book of Changes, could in fact be called the Bible of Sexism ("she should not give in to her whim; she should stay inside and prepare dinner"). The text is proto-Confucian, i.e. hierarchical and conservative, and finds its fullness in the Confucian commentary The Ten Wings, a text said to have "bewitched" Chinese civilization for more than 2,000 years. Likewise, it is historically not about commoners but about the upper class, and not about spirituality but about politics. Indeed, it is essentially a justification of the Zhou vassals' coup d'état, -11th century, grabbing the "Heavenly Mandate" from their suzerain, the Shang emperor, in response to an unexpected solar eclipse interpreted a s sign from Heaven to strike forthwith.
It is only in the Daoist classics by Laozi and Zhuangzi, some 500 years after the Book of Changes, that we get a Yin-friendly corrective. It has always been only a dissident counterstream, though a necessary counterpoint as per the Yin/Yang philosophy itself. But even that current does not teach "equality": Yin (dark, feminine, empty, hidden, soft, flexible) is so important and indispensible precisely because it is the opposite of Yang and allows Yang to shine.
This is clearest when we read Yin and Yang in their basic meanings: shadowy c.q. bright. As per Isaac Newton's optics, light and darkness are of a different nature: light is something, it has specific measurable properties, whereas darkness is nothing except the absence of light. (We find a counter-view in Johann Wolfgang von Goethe's optics, where darkness is seen as an entity in itself; but except in Rudolf Steiner's Anthroposophy, it never caught on.) The Yin/Yang doctrine is a more philosophical elaboration of the preceding Shang period's solar cult, in which the sunlight was desirable and the clouds were merely what came in the sunrays' way, hence undesirable. Whether we like it or not, such was the old school.