[Bells ringing] Thoreau graduated from Harvard College on August 30, 1837.

It was a time of significant change.

♪ Political issues, particularly slavery, were dividing states, communities, and even families.

The Industrial Revolution and the westward expansion of the country were reshaping the lives of many Americans.

Those in the younger generation often had to choose between settling further west, where farmland was more plentiful, or moving into the cities to work in factories.

Robert A. Gross: This is a generation for whom there's no single clear path to follow.

There's not enough land in Concord anymore for most farmers to set up their kids.

Bill McKibben: Mills going up everywhere up and down Massachusetts and New Hampshire, people streaming off the farm to work in those factories, being forced into worlds that they did not understand and were not suited for them.

Thoreau understood what it would mean to the human spirit.

♪ Narrator: In his senior year, Henry had read a book called "Nature" written by a 34-year-old philosopher and fellow citizen of Concord named Ralph Waldo Emerson.

In it, he spelled out an entirely new and radical approach to life.

♪ Ralph Waldo Emerson: The foregoing generations beheld God and nature face to face.

Why should not we also enjoy an original relation to the universe?

Why should not we have a poetry and philosophy of insight and not of tradition, and a religion by revelation to us, and not the history of theirs?

There are new lands, new men, new thoughts.

Let us demand our own works and laws and worship.

Narrator: Emerson had graduated from Harvard Divinity School and later served as a minister in Boston.

He then left the church for a new kind of ministry, an electrifying, spiritual, philosophical, and social movement that was attracting reformers and intellectuals dissatisfied with society's values.

It was called transcendentalism.

Lawrence Buell: Transcendentalism is the first youth movement in American history.

It was a reform movement to incinerate orthodoxies and rebuild from the idea that the individual genius trumped received wisdom.

That was music to Thoreau's ears.

Laura Dassow Walls: Transcendentalism boils down to one very simple but very powerful idea-- that there is a spark of divinity within absolutely every single human being.

[Birds chirping] That means every person who is enslaved, you are enslaving part and particle of God.

Every woman who doesn't have full human rights, every child that you're depriving of an education, you're depriving that spark from developing.

Rochelle L. Johnson: They're questioning religion, education, politics.

They're asking questions about labor and freedom and enslavement.

They're questioning the entire grounds of society.

That's pretty radical.

Narrator: Emerson's book "Nature" had established him as the leader of this new movement.

Henry, now 20 years old, became his protege.

"I delight much in my young friend," Emerson wrote, "who seems to have as free and erect a mind as any I've ever met."

Ralph Waldo Emerson: Brave Henry is content to live now and feels no shame in not studying any profession, for he does not postpone his life, but lives already, and pours contempt on these crybabies of routine and Boston.

Narrator: Emerson saw Thoreau's potential as a writer and encouraged him, asking, "What are you doing now?

Do you keep a journal?"

On October 22, 1837, Thoreau wrote, "I make my first entry today."

Laura Dassow Walls: His journal was meant to catch the flow of thoughts, of observations, and take that little emergent flame of whatever little spark is there and just explore it.