It thus could mean the shaded, north side of a mountain or the shaded, south bank of a river. From these basic opposites, a complete system of opposites was elaborated. Yin represents everything about the world that is dark, hidden, passive, receptive, yielding, cool, soft, and feminine. Yang represents everything about the world that is illuminated, evident, active, aggressive, controlling, hot, hard, and masculine. Everything in the world can be identified with either yin or yang.
Earth is the ultimate yin object.
Heaven is the ultimate yang object. Although it is correct to see yin as feminine and yang as masculine, everything in the world is really a mixture of the two, which means that female beings may actually be mostly yang and male beings may actually be mostly yin. Because of that, things that we might expect to be female or male because they clearly represent yin or yang, may turn out to be the opposite instead. Taoism takes the doctrine of yin and yang, and includes it in its own theory of change. Like Anaximander and Heraclitus, Taoism sees all change as one opposite replacing the other.