"It has often been said that, if the human species fails to make a go of it here on the Earth, some other species will take over the running. In the sense of developing intelligence this is not correct. We have or soon will have, exhausted the necessary physical prerequisites so far as this planet is concerned. With coal gone, oil gone, high-grade metallic ores gone, no species however competent can make the long climb from primitive conditions to high-level technology. This is a one-shot affair. If we fail, this planetary system fails so far as intelligence is concerned."

“Once we see, however, that the probability of life originating at random is so utterly minuscule as to make it absurd, it becomes sensible to think that the favorable properties of physics on which life depends are in every respect deliberate … . It is therefore almost inevitable that our own measure of intelligence must reflect … higher intelligences … even to the limit of God … such a theory is so obvious that one wonders why it is not widely accepted as being self-evident. The reasons are psychological rather than scientific.”

“To achieve anything really worthwhile in research it is necessary to go against the opinions of one's fellows. To do so successfully, not merely becoming a crackpot, requires fine judgement, especially on long-term issues that cannot be settled quickly. ...To hold popular opinion is cheap, costing nothing in reputation, whereas to accept that there is evidence pointing oppositely... is to risk scientific tar and feathers. Yet not to take the risk is to make certain that, if something new is really there, you won't be the one to find it.”

“When I was young, the old regarded me as an outrageous young fellow, and now that I'm old the young regard me as an outrageous old fellow.”

“I do not see any sense in continuing to skirmish on a battlefield where I can never hope to win. The Cambridge system is effectively designed to prevent one ever establishing a directed policy — key decisions can be upset by ill-informed and politically motivated committees. To be effective in this system one must for ever be watching one's colleagues, almost like a Robespierre spy system. If one does so, then of course little time is left for any real science.”

“The notion that not only the biopolymer but the operating program of a living cell could be arrived at by chance in a primordial organic soup here on the Earth is evidently nonsense of a high order.”

“Once a photograph of the Earth, taken from outside, is available, we shall, in an emotional sense, acquire an additional dimension... Once let the sheer isolation of the Earth become plain to every man, whatever his nationality or creed, and a new idea as powerful as any in history will be let loose.”