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No one can live entirely on their own, nor can any country or society exist in isolation.

I don't think the planet can survive people. It's not the other way around. I don't think the planet can survive.

Mars is the only place in the solar system where it's possible for life to become multi-planetarian.

The earth has a life of its own.

Just as the earth is a planet in its own right, so each of us is an individual in our own sphere of habitation. We are individuals, but we live in families and communities where order provides a system of harmony that hinges on obedience to principles.

It might be arrogant to think that we're the only living creations in all of the solar systems that there are. Space is so vast.

There's life all over this universe, but the only life in the solar system is on earth, and in the whole universe we are the only men.

It's very exciting that people could actually live on another planet.

There are too many accidents that can befall life on a single planet.

We're not going to persuade people in the developing world to go without, but neither can we afford a planet on which everyone lives like an American. Billions more people living in suburbs and driving SUVs to shopping malls is a recipe for planetary suicide. We can't even afford to continue that way of life ourselves.