He never says it. But it's a sequel, par excellence, to the classic _Cosmos_.
Sequels are usually disappointing. This is one of those rare cases where the sequel is better than the original. I had read this book in hardcover and ended up buying my own paperback copy while in Ithaca (Sagan's hometown) because I had nothing to read and a long ride back home.
I'm a fan of Sagan - can't help it - because even though he's a brilliant scientist, he somehow manages to be a great writer as well. This book is no exception. Sagan's basic idea is that the destiny of humanity is to expand out to the stars. And even though this idea reeks with echoes of Manifest Destiny, I have to agree. In Manifest Destiny, there were Indians - here, no intelligent life that we know of. And if there is something out there, wouldn't we want to know about it?
Like so many great works of popular science, Sagan starts out by tracing the changes in our views of the world, from our conceit that we were the center of the Universe to the backwater position that we're in today. Sagan's idea of generalized chauvinisms comes up - first in place (the obvious), then in time (if there was other intelligent life, it's not around any more), and, if I recall correctly, in chemical basis (life must be made out of carbon). He refutes all these ideas - and why not? Who said that silicon can't conquer the universe?
My personal favorite part of the book is Chapter 5, "Is There Intelligent Life On Earth?" Sagan asks us to "[imagine yourself as] an alien explorer entering the Solar system after a long journey through the blackness of interstellar space". As we examine the Earth at finer and finer resolution, what do we see? I won't tell you - it's a bit unexpected - but the answer will surprise you. Who said scientists can't be humorous?
A large portion of the book surveys the prospects of life elsewhere in the Solar System - Venus, Mars, Io, and Titan (but, surprisingly, not Europa) figure prominently. (Sagan did research on Titan tholins, precursors to organic molecules found on Titan.) It's interesting - maybe a bit out of place in Sagan's overall idea, but who cares?
So why don't we leave Earth? Why are we still stuck on this pale blue dot? The politicians, says Sagan. They don't see far enough into the future - all they care about is their own re-election. And it's even too far for normal humans to see, sometimes. But it's worth it - evolution demands that we adapt.
Near the end, we find this passage:
"It will not be we who reach Alpha Centauri and the other nearby stars. It will be a species very much like us, but with more of our strengths and fewer of our weaknesses, a species returned to circumstances more like those for which it was originally evolved, more confident, farseeing, capable, and prudent - the sorts of beings we would want to represent us in a Universe that, for all we know, is filled with species much older, much more powerful, and very different." (p. 329) Perhaps this illustrates the inspirational quality of Sagan's writing. So why are we still here?