The range of the mind's eye is restricted by the skill of the hand. The castles in the air must conform to the possibilities of material things -- border-line possibilities perhaps; or, if something beyond the known border is required, the plan must wait until other dreams come true.
Harry Brearley, inventor of stainless steel, from his memoir (reprinted in Nautilus, May/June 2016, p. 35)
In corporate religions as in others, the heretic must be cast out not because of the probability that he is wrong but because of the possibility that he is right.
Antony Jay (reprinted in https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/EWD831.html)
The Stone Age did not end for lack of stone, and the Oil Age will end long before the world runs out of oil.
Sheikh Zaki Yamani, a former Saudi oil minister (quoted in https://news.ycombinator.com/item?id=13740735).