The Achilles 'heel--passion According to Daoist doctrine, anyone who masters the necessary Daoist arts can live for thousands of years, and average believers go even further, holding that any thing can change its appearance. The white snake, for example, is thought to be capable of training itself to appear as a human.
道教神仙理論更認為，透過一套技術修煉，生命可以常保千年之身，經過民間轉化，成為萬物可自由轉換自己面貌，如白蛇可修煉成人形。