Early in If a Tree Falls, we see footage of a protester sitting high in a tree that the City of Eugene intends to cut down. All the protester is trying to do is stall until the next day, when a city council meeting is scheduled to discuss the removal of the tree - a removal which was moved up so that it would take place before the council meeting. In response to this peaceful protest, police approach the man in the tree via a cherry picker, cut open his pants and spray his thighs and genitals with pepper spray. He is roughly 40 feet in the air, without any cushioning below him, and he is being bombarded with an irritant that could cause him to fall to the concrete. After staying up for a few more hours, he finally relinquishes and climbs to the ground, where he is washed off and arrested, and the tree is cut down.

It's moments like these - of which there are several in If a Tree Falls - that make it easier to understand how a group of environmental activists made the transition from peaceful protests to the targeted destruction of environmentally harmful buildings. These activists would come to be known as the Earth Liberation Front (ELF), and they utilize arson in their attacks on buildings like lumber yards and sites for genetic engineering on trees. The documentary mainly follows Daniel McGowan, one of the members of ELF, as he sits under house arrest, awaiting a verdict that could mean up to a life sentence for eco-terrorism.

The main strength of If a Tree Falls is the way that it plays with who we side with at any given moment. While the film is certainly sympathetic to the members of ELF and their good intentions, it doesn't shy away from the real, violent nature of what they're doing (even though ELF never physically harmed anyone and always made sure the buildings were empty when they were set ablaze) and the errors that they made - including the accidental destruction of a University of Washington library and the burning of a farm that ELF mistakenly thought was being used for genetic engineering.

"(The opportunity to make the film) sort of dropped in my lap," says Director Marshall Curry. "My wife runs a domestic violence organization in Brooklyn, and came home from work one day and told me that four federal agents had walked into her office that day and arrested one of her employees, who was this guy, Daniel McGowan."

In Daniel McGowan, Curry found a seemingly completely sensible subject - one capable of self-reflection and conflicted feelings about his crimes. He still believes in the core truth of his cause, but as former ELF members begin to cooperate with the FBI, his spirits begin to sag, and the realization that he may be labeled a terrorist and head to prison for the rest of his life begins to weigh on him.

A discussion arises late in the film about whether the members of ELF deserve to be labeled "terrorists." This distinction becomes more pressing as McGowan learns that - if convicted as a terrorist - he will be confined to a special, very restricted prison reserved for convicted terrorists. The argument comes down to whether terrorism should be interpreted as causing harm to others, or merely instilling fear. As arsonists, I think it's pretty clear that fear was one of the unspoken goals of ELF.

"Every time we talked to somebody, on both sides, our point of view stretched," says Curry. "When we sat down to edit, we decided to try and build that experience into the movie itself - to take an audience on that same journey."

If a Tree Falls is a fascinating and sure-to-be-divisive film - and one that should be talked about.