First appearance in The Magazine of Fantasy & Science Fiction, July 1965.
A ship with a two-man crew, a normal human Howie and Eric – a disembodied brain of a previously injured man taking the part of ship's computer, is exploring the upper atmosphere of Venus, using the empty fuel-tank as a dirigible device.
About to return to Earth, Eric reveals that something is wrong with the ramjet that propels the craft, necessitating a landing in order to fix the problem. When Howie can find nothing physically wrong with the system, he can only conclude that, disturbingly, the problem is with Eric. He believes Eric has a psychosomatic disorder preventing him from operating the ramjets, using the analogy of a traumatized soldier that can no longer feel his hand and pull the trigger of a gun.
After revealing his theory to Eric, Eric admits it is a possibility but insists that Howie keep inspecting the ship, reasoning that Howie is the only one that can check for mechanical problems. Howie agrees, but secretly has convinced himself that the problem is truly with Eric.
In an effort to cure Eric using a placebo, Howie creates buckets of ice-water using the ship's freezer, and dumps it into the wiring panels on the wings, telling Eric that the heat and pressure of Venus might be affecting the ships function. Eric regains the use of the ramjets and the pair manage to escape from Venus and back to Earth.
On the trip back, Howie reveals his ruse to Eric. Eric insists that the cause was mechanical, and challenges Howie to a $5,000 bet that the problem will be found back on Earth. Howie accepts the bet. Back on Earth, the mechanics determine that, indeed, it was a mechanical problem due to the pressure of Venus's atmosphere.
Published in several collections: All the Myriad Ways (1969, coll), Inconstant Moon (1973, coll), Tales of Known Space: The Universe of Larry Niven (1975, coll), Playgrounds of the Mind (1990, coll), Three Books of Known Space (1996, coll)