What if a tree fell in the woods but . . . 

1 . . . nobody heard.

Could you really say that a tree had fallen?

2 . . . one man heard and  was struck by the falling tree and died on the spot.

While the man was alive, could you say that a tree had fallen, but after he was killed, that a tree had never fallen?

3 . . . one man heard, then was struck by the falling tree and fell into a deep unconscious coma, only to awaken six months later with a full memory of the tree falling.

While the man was in a coma, could you say that no tree had fallen, but after he regained his memory, could you say that a tree had fallen?

4 . . . one man heard, then was struck by the falling tree and fell into a deep unconscious coma from which he has not yet recovered.

Could you say that no tree has fallen, but that if the man recovers, a tree will have fallen?

5 . . . though no-one heard it, the sound was recorded by a minidisc recorder and sent on a T1 dedicated line up to iTunes. Unfortunately a couple bytes at the start of the digital sequence were scrambled so a million people downloading it to their iPods heard only random noise. It is unlikely that the data will ever be recovered and made intelligible unless a highly skilled person does a lot of work on it, and even then she will have to be lucky as well.

Could you say . . . anything?

6 . . . nobody knows if anyone heard it fall or not.

Is it possible that the tree may have fallen?

7 . . . the person who claims to have heard it fall is notoriously unreliable.

Must you then deny that it has fallen?

8 . . . nobody heard it fall. However, someone heard a different tree fall and mistook it for the first.

Could you say that a tree had fallen, though you would be mistaken?