Daoist thought prior to Qin dynasty (pre-221 BC)
Prior to the Qin dynasty, Daoism was a school of thought and not a religion. ''Laozi'' and ''Zhuangzi'' were originally philosophical works and not religious scriptures: that they later came to be counted among the doctrinal foundations of religious Daoism ( 道教 Daojiao) is the result of a historical process by which the emerging Daoist religion actively made use of the early Daoist philosophical works. Early Daoist philosophy ( 道家 Daojia) provides a wide choice of concepts suited to becoming the foundation of Daoist religious teachings. For example, Daoist philosophy attaches special importance to Nurturing Life ( 養生 Yangsheng) as well as to longevity. For instance, the Laozi states: "the spirit that is cultivated does not die", and "Dao is immortality and omniscience". According to the Zhuangzi, if one does not exhaust one's body or trouble one's spirit, one can attain immortality, leave this world of dust, ascend to the concourse of Immortals ( 神仙 Shenxian ), and ride on clouds to the Realm of Divinity. These ideas later became the conceptual basis of the Immortalist ideology of later religious Daoism. The concept of 'Dao' in pre-Qin Daoist philosophy has mysterious connotations; religious Daoism later further mystified the concept to the point of deifying and personifying it, turning Dao into a Creator possessing willpower and feeling. This led to Daoist philosophy entering the realm of religious theology.
Some scholars consider that the philosophy of Laozi and Zhuangzi share a common origin with primitive religion, and that philosophical and religious Daoism stem from a common archaic religious source. Consequently, there is an intimate relationship between the two, and religious Daoism is the continuation of philosophical Daoism. This relationship represents the juncture between pre-Qin Daoist philosophy and later religious Daoism.
The history of Daoist philosophy can been seen as developing in three stages: Pre-Qin Lao-Zhuang philosophical Daoism (exemplified by the Laozi and Zhuangzi, prior to 221 BC), Qin and Han dynasty Huang-Lao philosophical Daoism (221 BC - 220 AD), and the mystical Daoism of the Wei and Jin dynasties (220 - 420 AD). Pre-Qin Daoist philosophy is the conceptual foundation of the teachings of later religious Daoism; Huang-Lao Daoist philosophy represents a crucial stage in its evolutionary development. In modern times, the historian Meng Wentong pointed out in his Discussion of Daoist History that following the Wei and Jin dynasties (220 - 420 AD), the Laozi and Zhuangzi became accepted as scripture by all disciples of Daoist religion, and were regarded as the essence of Daoist religious philosophy. It is impossible to speak of Daoism while ignoring the Laozi and Zhuangzi. Pre-Qin Daoist philosophical thought is the primary source of later Daoist religious thought.