Teaching has never been far from my life. It's the most natural thing I do. Apparently, as I said, I cannot not do it.

That statement [ Stephen Ambrose:'You, Sam, have the hardest job, which is, pretend like nothing has happened in the last 200 years.'] woke me up to the fact that the landscape that Lewis and Clark came across was greater than the Serengeti. And it's gone.

It's a little bit like talking about the life of writing. The life of writing may be about many things, but it always begins with the writer. With the kernel of an idea, or a character, or an idea or a theme, or even an outcome. But for documentary photographers, photographs begin at that intersection of the real world and the imaginative inner world.

It's more difficult now, to be a Geographic photographer, than it was when I came along. And it wasn't easy at that time.

I was asked by a student what my most significant accomplishment was at National Geographic, after thirty years, and I said that my career came to an appropriate close, and I still loved photography. Not everybody who spends their career at anything ends up fascinated and involved with it.

I think of myself as a writer who photographs. Images, for me, can be considered poems, short stories or essays. And I've always thought the best place for my photographs was inside books of my own creation.

Life rarely presents fully finished photographs. An image evolves, often from a single strand of visual interest - a distant horizon, a moment of light, a held expression.