The doubter is a true man of science; he doubts only himself and his interpretations, but he believes in science. – Claude Bernard

Observation is a passive science, experimentation an active science. – Claude Bernard
A fact in itself is nothing. It is valuable only for the idea attached to it, or for the proof which it furnishes. – Claude Bernard
What I like about sceptics is that in good science you need critics that make you think: Crumbs, have I made a mistake here? If you dont have that continuously, you really are up the creek. The good sceptics have done a good service, but some of the mad ones I think have not done anyone any favours. – James Lovelock
A permanent base on Mars would have a number of advantages beyond being a bonanza for planetary science and geology. If, as some evidence suggests, exotic micro-organisms have arisen independently of terrestrial life, studying them could revolutionise biology, medicine and biotechnology. – Paul Davies