The term refers to the fundamental state of the existence of things. Bian (变) and hua (化) may be used as one word or separately. Specifically, bian means manifest change, while hua indicates subtle and gradual change. Ancient Chinese thinkers generally held that all things under heaven and on earth, including humans and society, are all in a state of change. Only through constant change can they permanently exist and develop. Change is caused by constant clash and integration between the conflicting properties with which people and things are endowed. Some scholars believed that change follows a constant law and can thus be understood and grasped, while others maintained that change is unpredictable and therefore difficult to grasp. Buddhism, on the other hand, holds that changes of things are only superficial, and that all things are still and motionless.