In the Fellowship of the Ring, why was the Old Forest able to respond to what the hobbits said or did? The forest is not composed of Ents, which can think, feel, and walk, yet the trees shift and change the paths and make ominous noises. Is this just a result of the hobbits imagination and fears?
Pippin suddenly felt that he could not bear it any longer, and without warning let out a shout. 'Oi! Oi!' he cried. 'I am not going to do anything. Just let me pass through, will you!' The others halted startled; but the cry fell as if muffled by a heavy curtain. There was no echo or answer though the wood seemed to become more crowded and more watchful than before.
This is right before they find the Bonfire Glade:
But at that moment Merry gave a whistle of relief and pointed ahead. "Well, well!" he said. "These trees do shift. There is the Bonfire Glade in front of us (or I hope so), but the path to it seems to have moved away!"
(emphasis and parenthesis not mine.)
The third example is under Old Man Willow, yet another example of unexplained movements and actions by trees. Frodo and Sam are setting a fire near the tree. Apparently the tree can talk, at least to those inside it.
"Do you know, Sam," (Frodo) said at length, "the beastly tree threw me in! I felt it. The big root just twisted round and tipped me in!"
(emphasis not mine. Parenthesis mine.)
Merry was trapped: another crack had closed about his waist; his legs lay outside, but the rest of him was inside a dark opening, the edges of which gripped like a pair of pincers.
"Put it out! Put it out!" cried Merry. "He'll squeeze me in two, if you don't. He says so!"
Finally, why can these trees move of their own accord? Is it some great evil being controlling them and trying to obstruct the hobbits and the Ring from reaching Rivendell?