"We’re all depressingly ‘lay’ outside our specialisms — my own knowledge, of recent biological advances, such as it is, comes largely from ‘popular’ books and journalism."

“Absence of evidence is not evidence of absence.”

“Once the threshold is crossed when there is a self-sustaining level of life in space, then life's long-range future will be secure irrespective of any of the risks on Earth . Will this happen before our technical civilisation disintegrates, leaving this as a might-have-been? Will the self-sustaining space communities be established before a catastrophe sets back the prospect of any such enterprise, perhaps foreclosing it for ever? We live at what could be a defining moment for the cosmos, not just for our Earth.”

“2005 TED talk: Is this our final century?”

“Our Universe and Others”

“No one can say which approach is the right one — so no one can say how close we are to a solution.”

“Interviews with Charlie Rose, 2003 and 2008”