The source of living can be found in "xh'aséikw", the essence of life. This bears some resemblance to the Chinese concept of qi as a metaphysical energy without which a thing is not alive; however in Tlingit thought, this can be equated to the breath as well. For example, the shaman's simplest test for whether a person is alive is to hold a downy feather above the mouth or nose; if the feather is disturbed then the person is breathing and alive, even if the breath is not audible or sensible. This then implies that the person still maintains "x̲'aséikw".