A very heavy
book by John D. Barrow
, Frank A. Tipler
and John A. Wheeler
The book discusses cosmological arguments from a philosophical viewpoint,
but also relies heavily on scientific evidence to illustrate how stupendously unlikely a life-bearing Universe is.
It then investigates why we live in best of all possible worlds, (where 'best' = capable of supporting life).
One of the more interesting theories discussed here is a quantum-mechanical explanation of the Universe.
This combines the arguments of the Schrodinger's Cat thought experiment with Many Worlds theory to explain the Universe's existence.
Many world theory states that there are an infinite number of possible worlds, corresponding to quantum probablility wavefunctions.
(Toss a coin. One possible world = heads, the other = tails.
Neither is more 'real' than the other. It sounds stupid,
but that's how the Universe works at its smallest level. Don't blame me.)
So there are an infinite number of possible Universes.
Since an observer is needed to collapse a probability waveform into reality,
(i.e. "nothing exists until you look at it")
the only possible Universes that can exist are the ones that have observers in them i.e.
those containing intelligent/conscious lifeforms - all the others never acheive reality precisely because they are dead.
To sum up:
"The Universe contains intelligent life because without it , it couldn't exist."