EXPLORING the world is one of the best ways of exploring the mind, and walking travels both terrains.

For millions of years, this world has been a great gift to nearly everything living on it, a planet whose atmosphere, temperature, air, water, seasons, and weather were precisely calibrated to allow us - the big us, including forests and oceans, species large and small - to flourish.

A lot of people think of political activism as some grim duty, and I think we do have an obligation to be citizens - to be informed and engaged.

Perhaps the central question about [Eliot] Porter's work is about the relationship between science, aesthetics, and environmental politics. His brother, the painter and critic Fairfield Porter, wrote in a 1960 review of [Porter's] colour photographs: 'There is no subject and background, every corner is alive,' and this suggests what an ecological aesthetic might look like.

How will you go about finding that thing the nature of which is totally unknown to you?

The power of large corporations is still a scourge on the earth, but at least the arguments supporting them are undermined now.

Lost really has two disparate meanings. Losing things is about the familiar falling away, getting lost is about the unfamiliar appearing.