Dao is often called as “The Way”, understood as a “Flowing Principle”, but in traditional Daoism from Alchemical perspective, what does 道 really mean? People have all kinds of interpretations, most of them incorrect.
Being one with the Natural principle of things is Human Dao (人道Ren Dao). To lose Dao is to lose Human Dao first of all. It means people stop following the changes of Nature, they lost something what allows them to do it. Neidan (Internal Alchemy) is just another name for Celestial Dao (天道 Tian Dao), which is Lao Zi’s Great Dao (大道 Da Dao) which is not the same as Human Dao. it’s a totally opposite thing. Celestial Dao is what Daoism really teaches to follow. There are clear definitions in Dao De Jing, but people prefer to sing songs about being one with Nature and to say Daoism is to follow the Dao of things (natural way).
People are born, grow, get various experiences, skills, do some work, get some pleasures and sufferings, then die. that is the Dao of things but not the Da Dao / Tian Dao.
Dao is a source of everything, it can be found everywhere.
But what was born out of Dao is not Dao anymore. Humans are not Dao, but they have Dao. If humans are already Dao, then there is no need in Dao as a practice. if they have Dao (Ren Dao), they have to “cultivate Da Dao” and “attain Da Dao”. If they lost Dao, they “don’t live long”. It’s not possible to understand if we only think Dao means “way” or if Dao is a principal or philosophy.
So Dao is unknown source of life. We cannot know it, but we can realize it (through the practice of alchemy). All texts and words are to help people to start the way, find a True Teacher and follow the Teacher (methods and so on), but not follow the Dao itself (the Natural way), in Neidan the Dao it self is not followed, but the Great Dao is acquired inside of own body. If the Dao is merely followed it follows the natural principal of creation and destruction – which is the pathway of the mundane and ordinary person, which is not Laozi’s Great Celestial Dao.