The End of Eternity by Isaac Asimov

governments in every Century are forever forwarding applications to Eternity to ‘please, pretty please ship them seventy-five thousand ampules of serum on behalf of the men critically stricken who are absolutely vital to the cultures, enclosed see biographical data.’ ”
    Voy nodded rapidly, “I know. I know.”
    But Feruque was not to be denied his bitterness. “So you read the biographical data and it’s every man a hero. Every man an insupportable loss to his world. So you work it through. You see what would happen to Reality if eachman lived, and for Time’s sake, if different
combinations
of men lived.
    “In the last month, I’ve done 572 cancer requests. Seventeen, count them, seventeen Life-Plots came out to involve no undesirable Reality Changes. Mind you, there wasn’t one case of a possible
desirable
Reality Change, but the Council says neutral cases get the serum. Humanity, you know. So exactly seventeen people in assorted Centuries get cured this month.
    “And what happens? Are the Centuries happy? Not on your life. One man gets cured and a dozen, same country, same Time, don’t. Everyone says, Why
that
one? Maybe the guys we didn’t treat are better characters, maybe they’re rosy-cheeked philanthropists beloved by all, while the one man we cure kicks his aged mother all around the block whenever he can spare the time from beating his kids. They don’t know about Reality Changes and we can’t tell them.
    “We’re just making trouble for ourselves, Voy, unless the Allwhen Council decides to screen all applications and approve only those which result in a desirable Reality Change. That’s all. Either curing them does some good for humanity, or else it’s out. Never mind this business of saying: ‘Well, it does no harm.’ ”
    The Sociologist had been listening with a look of mild pain on his face, and now he said, “If it were
you
with cancer . . .”
    “That’s a stupid remark, Voy. Is that what we base decisions on? In that case there’d never be a Reality Change. Some poor sucker always gets it in the neck, doesn’t he? Suppose you were that sucker, hey?
    “And another thing. Just remember that every time we make a Reality Change it’s harder to find a good next one. Every physioyear, the chance that a random Change is likely to be for the worse increases. That means the proportionof guys we can cure gets smaller anyway. It’s always going to get smaller. Someday, we’ll be able to cure only one guy a physioyear, even counting the neutral cases. Remember that.”
    Harlan lost even the faintest interest. This was the type of griping that went with the business. The Psychologists and Sociologists, in their rare introvertive studies of Eternity, called it identification. Men identified themselves with the Century with which they were associated professionally. Its battles, all too often, became their own battles.
    Eternity fought the devil of identification as best it could. No man could be assigned to any Section within two Centuries of his homewhen, to make identification harder. Preference was given to Centuries with cultures markedly different from that of their homewhen. (Harlan thought of Finge and the 482nd.) What was more, their assignments were shifted as often as their reactions grew suspect. (Harlan wouldn’t give a 50th Century grafenpiece for Feruque’s chances of retaining this assignment longer than another physioyear at the outside.)
    And still men identified out of a silly yearning for a home in Time (the Time-wish; everyone knew about it). For some reason this was particularly true in Centuries with space-travel. It was something that should be investigated and would be but for Eternity’s chronic reluctance to turn its eyes inward.
    A month earlier Harlan might have despised Feruque as a blustering sentimentalist, a petulant oaf who eased the pain of watching the electro-gravitics lose intensity in a new Reality by railing against those of other Centuries who