In Book 3, the "Qi" is mentioned by the Chinese sailors, refering to their "soul" or "life force".

Qi, (Traditional Chinese: 氣, Simplified Chinese: 气, Japanese: 気) also commonly spelled ch'i (in Wade-Giles romanization) or ki (in romanized Japanese), is a fundamental concept of traditional Chinese culture. Qi is believed to be part of everything that exists, as in “life force” or “spiritual energy,” It is most often translated as “energy flow,” or literally as “air” or “breath” (for example, a term meaning “weather” is tiānqì (Traditional Chinese: 天氣, Simplified Chinese: 天气), literally “sky air”). It is pronounced something like "chee" in Mandarin Chinese but the tongue position is different. (See Media:Difficult Sounds.GIF.)The etymological meaning of the qi logogram in its traditional form 氣 is “steam (气) rising from rice (米) as it cooks.”References to qi, and similar philosophical concepts, as the life-process of “flow” in metaphysical energy that sustains living beings are found in many belief systems, especially in Asia. Philosophical conceptions of qi date from the earliest recorded times in Chinese thinking. One of the important early figures in Chinese mythology is Huang Di (the Yellow Emperor). He is often considered a culture hero who collected and formalized much of what subsequently became known as traditional Chinese medicine.Although the concept of qi has been very important within many Chinese philosophies, their descriptions of qi have been varied and conflicting. One significant difference has been the question of whether qi exists as a force separate from matter, if qi arises from matter, or if matter arises from qi. Some Buddhists and Taoists have tended toward the third belief, with some Buddhists in particular believing that matter is an illusion.By contrast, the Neo-Confucians criticized the notion that qi exists separate from matter, and viewed qi as arising from the properties of matter. Most of the theories of qi as a metaphor for the fundamental physical properties of the universe that we are familiar with today were systematized and promulgated in the last thousand years or so by the Neo-Confucians. Knowledge of the theories they espoused was eventually required by subsequent Chinese dynasties to pass their civil service examinations.

From the English Wikipedia article: Qi
Character forms added by: pdelrio