"We each live in a somewhat unique world of our own psychological content."
- Philip K. Dick

An earlier description of this notion can be found in The First Martian (1932) by Eando Binder:

The inconceivable distance to be traversed, the enormous energy required to transport a heavy machine from planet to planet, and the all-powerful force of gravity, seemed insurmountable objects to even the most broadminded and optimistic thinkers. Feeble attempts were made even in 1931 to leave this speck of the universe and soar to other worlds, but constant failures dulled the ardor of those who wished to connect our world with the others which acknowledge the same central sun... Although the fatalities far exceeded these probable successes, the hope of interplanetary travel was still uppermost in our minds. We know now, that our failure can be attributed to the unfortunate lack of radioactive elements, and not to the lack of ingenuity or inventiveness. It was only too true. as Professor Billings stated in 1945, that the only type of engine which could possibly transport a heavy machine from our earth to some planet, would have to be the atomic-energy engine, which, with a minimum of fuel and the very necessary radioactive element, could develop an unlimited amount of energy.

He even drew plans of the basic principles of such an engine, estimated the amount of radioactive material needed, and worked out the propulsion of the ship.

Compare to these propulsion systems: Light Pressure Propulsion (1867), apergy (1880), Beam-Powered Propulsion (1931), Granton motor (1933), Vibration-Propelled Cruiser (1928), geodynes (1936), ion drive (1947), Planetary Propulsion-Blasts (1934), stardrive (1953), solar sail (light sail) (1962), Lyle drive (1961), laser cannon (1966), Bussard ramjet (1976), asymptotic drive (1976), Interstellar Laser Propulsion System (1985).