The woods are an ominous and scary place in European fairytale tradition. It harbors witches and threatening animals. Children get lost or marooned by their parents. At the same time they house the little birds and friendly eremites, people who are willingly good and helpful.
Whose woods these are I think I know.
His house is in the village though;
He will not see me stopping here
To watch his woods fill up with snow.
My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.
He gives his harness bells a shake
To ask if there is some mistake.
The only other sound’s the sweep
Of easy wind and downy flake.
The woods are lovely, dark and deep.
But I have promises to keep,
And miles to go before I sleep,
And miles to go before I sleep.
Stopping by Woods on a Snowy Evening
By Robert Frost 1923
The living things hide themselves in the woods, then we can not make sure of their exist. They appear as the deep and big woods in our imagination, and always come in contact with our world.
The overabundance of the power of spiritual beings is truly amazing. Looking for them, they cannot be seen. Listening for them, they cannot be heard. There is nothing that they do not embody. They cause the people of the world to fast for purification, and wear beautiful clothes in order to participate at the sacrifices. They are overflowing, seeming to be above, seeming to be on the left and on the right.
（The Doctrine of the Mean, chapter 16.）