(inspiring music) - [Narrator] His life was a relentless search for truth.

His words have inspired revolutions, social movements, and environmental actions all around the world for more than 150 years.

His name was Henry David Thoreau.

(soft dramatic music) - [Narrator 2] I wanted to live deep and suck out all the marrow of life, to live so steadily and Spartan-like as to put to route all that was not life, to drive life into a corner and reduce it to its lowest terms, and if it proved to be mean, rather than to get the whole and genuine meanness of it and publish its meanness to the world.

Or if it were sublime, to know it by experience and be able to give a true account of it in my next excursion.

- Most people today would say, why am I not happy?

They realized that the path that they took to happiness has not precisely worked out for them.

Thoreau was trying to make sense of life.

He lived exactly the way he wanted to live, and there was an enormous freedom for him that most people just don't get.

The things he's getting at were mostly ignored then, and they're mostly ignored now.

But Thoreau understood that language matters.