Through an examination of the meaning of the term 寒 Han/Cold, we can intimate that it is not only the pathogenic factor Cold, nor even the exterior pathogenic influences that the Shang Han Lun describes. Indeed, anything that inhibits the expression of Yang (even its growth maturation, eventual decline, and return to quiescence) can be described as injurious to the nourishment of life. And therefore, in the broadest sense cold can include the idea of anything deleterious to life. The central premise of this my understanding is best described as the Release and Return of Yang. And concern with the state of Yang in the body is of primary importance to the restoration of normal, healthy physiology.
Tracing a lifetime across a circle, just as the Sun seems to trace a circle through the sky, under the earth, and rising anew in the East, one sees that it is the vital spark of Yang that gives rise to life, Yang that allows the motion of inspiration and exhalation, the rising of Wood in the East, and the descending of Metal in the West, and ultimately moves one inevitably to return to a state of quiescent immersion in the Water that will extinguish the spark, and free the soul for release into the One. Thus, when one looks into the mystery of this cycle, all manifestations of evolution and becoming rely on the Yang being "commanded to the Yin."