Tao and the Heavenly Nature
The "Way of Heaven" is a mysterious syntagm very much discussed by the sinologists. The meaning of this syntagm is clearly revealed by a passage of the book Chuang-tzu:
"What do you mean," pursued the earl, "by the Heavenly, and by the Human?" Zo replied, "Oxen and horses have four feet; - that is what I call their Heavenly (constitution). When horses' heads are haltered, and the noses of oxen are pierced, that is what I call (the doing of) Man. Hence it is said, <>". (Book XVII, Chap 7, Legge).
The "Heavenly constitution" is another name for Tao or for the "Way of Heaven". What we can understand from this short dialogue is that Taoists consider Tao a natural and usual concept of harmony and equilibrium of the essence of things in the Universe. What represents the natural part of a creature or of a phenomenon - not necessarily animated - is its very essence, and is alluded by the term Tao. The human being brings about, by his activity, essential changes to this "Way of Heaven". These changes - "human" ones - represent real deviations from the "Way of Heaven", and can become the opposite of the natural way of things.