When I was in school, we knew of no extra-solar planets. Now that we know how to look, they seem to be everywhere. Similarly, I suspect life will turn out to be common once we can send probes to the places that could harbour them.<p>Intelligent life might well be an order-of-magnitude rarer, and life intelligent enough to be detectable by SETI rarer still. (And we could well be the most advanced civilization in our light cone -- someone has to be.)