“Arthur Dent: What happens if I press this button?
Ford Prefect: I wouldn't-
Arthur Dent: Oh.
Ford Prefect: What happened?
Arthur Dent: A sign lit up, saying 'Please do not press this button again.”

Source: Books, Spiritual Warrior, Volume I: Uncovering Spiritual Truths in Psychic Phenomena (Hari-Nama Press, 1996), Chapter 4: Fire and Brimstone, Horns and Tail, p. 65

Source: So Long, and Thanks for All the Fish

'Blinding white flash'
Essays and reviews, Glued to the Box (1983)

Source: On Being Blonde (2007), p. 54

Source: Christopher and His Kind (1976), p. 335
Context: Suppose, Christopher now said to himself, I have a Nazi Army at my mercy. I can blow it up by pressing a button. The men in that Army are notorious for torturing and murdering civilians — all except for one of them, Heinz. Will I press the button? No — wait: Suppose I know that Heinz himself, out of cowardice or moral infection, has become as bad as they are and takes part in all their crimes? Will I press that button, even so? Christopher's answer, given without the slightest hesitation, was: Of course not.
That was a purely emotional reaction. But it helped Christopher think his way through to the next proposition. Suppose that Army goes into action and has just one casualty, Heinz himself. Will I press the button now and destroy his fellow criminals? No emotional reaction this time, but a clear answer, not to be evaded: Once I have refused to press that button because of Heinz, I can never press it. Because every man in that Army could be someone's Heinz and I have no right to play favorites. Thus Christopher was forced to recognize himself as a pacifist — although by an argument which he could only admit to with the greatest reluctance.

Source: The Hitchhiker's Guide to the Galaxy

Source: Vorkosigan Saga, Falling Free (1988), Chapter 15 (p. 284)

Artûs der meienbære man,
swaz man ie von dem gesprach,
zeinen pfinxten daz geschach,
odr in des meien bluomenzît.
Bk. 6, st. 281, line 16; p. 147.
Parzival