From natural phenomena and life experience, people gradually came to recognize the signs of change in a particular matter. For example, there was the ancients 'saying that "If the moon has a halo it will be windy, and a damp plinth foretells rain."
人們從自然現象和生活經驗中，漸漸認識一件事情變化的癥兆，像古人所謂的「月暈而風，礎潤而雨」，就是一例。