I certainly don't believe that the declassification yesterday of Ministry of Defence files reporting encounters with unidentified flying objects in British airspace shows that we have found aliens. But I am open-minded about the possibility and would dearly like to know if they exist.
...[But] even if intelligence were widespread, we may never become aware of more than a small and atypical fraction of what is out there.
Some brains may package reality in a fashion that we cannot conceive. Others could be living contemplative lives, doing nothing to reveal their presence. Absence of evidence would not be evidence of absence. The only type of intelligence we could detect would be one that led to a technology we could recognise.
I've always found Lord Rees to be one of the more contemplative and open-minded scientists engaging with the public. He has written at length of the dangers facing the world - not least those due to advances in science itself (see this TED talk he gave). And though a non-believer in the concept of 'God', he still regularly attends church because he enjoys the ritual and sense of community, and the sharing of a sense of wonder about the Universe. Sounds like someone I could have a beer with. Or at least a cup of tea.