“My mentality is that of a samurai. I would rather commit seppuku than fail.”

“I have made the mistaken assumption - and I will attempt to be better at this - of thinking that because somebody is on Twitter and is attacking me that it is open season. And that is my mistake.”

“I started SpaceX with the expectation of failure.”

“Even if producing CO2 was good for the environment, given that we're going to run out of hydrocarbons, we need to find some sustainable means of operating.”

“Optimism, pessimism, f**k that; we're going to make it happen. As God is my bloody witness, I'm hell-bent on making it work.”

“There is a world elsewhere.”

“We must be lovers, and at once the impossible becomes possible.”

“An infinity of forest lies dormant within the dreams on one acorn.”

“Be great in act, as you have been in thought.”

“My free drift Halts not particularly, but moves itself In a wide sea of wax; no levelled malice Infects one comma in the course I hold, But flies an eagle flight, bold and forth on, Leaving no tract behind.”

“Talking isn't doing. It is a kind of good deed to say well; and yet words are not deeds.”

“All life is an experiment. The more experiments you make the better.”

“The Good Spirit never cared for the colleges, and though all men and boys were now drilled in Greek, Latin, and Mathematics, it had quite left these shells high on the beach, and was creating and feeding other matters [science] at other ends of the world.”

“Nature is a rag-merchant, who works up every shred and ort and end into new creations; like a good chemist, whom I found, the other day, in his laboratory, converting his old shirts into pure white sugar.”