Entry in progress—B.P.
 
Wikipedia: Camel’s nose 
The camel’s nose is a metaphor for a situation where permitting some small undesirable situation will allow gradual and unavoidable worsening. A typical usage is this, from U.S. Senator Barry Goldwater in 1958:
 
This bill and the foregoing remarks of the majority remind me of an old Arabian proverb: “If the camel once gets his nose in the tent, his body will soon follow.” If adopted, the legislation will mark the inception of aid, supervision, and ultimately control of education in this country by the federal authorities.
 
According to Geoffrey Nunberg, the image entered the English language in the middle of the 19th century. An early example is a fable printed in 1858 in which an Arab miller allows a camel to stick its nose into his bedroom, then other parts of its body, until the camel is entirely inside and refuses to leave. Lydia Sigourney wrote another version, a widely reprinted poem for children, in which the camel enters a shop because the workman does not forbid it at any stage.
 
The 1858 example above says, “The Arabs repeat a fable,” and Sigourney says in a footnote, “To illustrate the danger of the first approach of evil habit, the Arabs have a proverb, “Beware of the camel’s nose”. However, Nunberg could not find an Arab source for the saying and suspected it was a Victorian invention.
 
An early citation with a tent is “The camel in the Arabian tale begged and received permission to insert his nose into the desert tent.” By 1878, the expression was familiar enough that part of the story could be left unstated. “It is the humble petition of the camel, who only asks that he may put his nose into the traveler’s tent. It is so pitiful, so modest, that we must needs relent and grant it.”
 
In a 1915 book of fables by Horace Scudder, the story, titled The Arab and His Camel, ends with the moral: “It is a wise rule to resist the beginnings of evil.”
 
There are a number of other metaphors and expressions which refer to small changes leading to chains of events with undesirable or unexpected consequences, differing in nuances.
 
. Foot in the door - a persuasion technique
. Slippery slope - an argument, sometimes fallacious
. “The thin end of the wedge”’
. Domino effect
. For Want of a Nail (proverb) - the claim that large consequences may follow from inattention to small details
. Boiling frog
. “Give them an inch; they’ll take a mile” The original saying goes “Give them an inch, and they’ll take an ell”.
. In Chinese culture, the “inch-mile” saying corresponds to the expression 得陇望蜀 (De Long Wang Shu), which is a quotation from the Book of Later Han about a Chinese general who took over Long (now Gansu) only to pursue further southwards into Shu (now Sichuan).
 
For comparison, positive consequences may start from small acts, and there is a similar set of sayings like Lao Tzu’s Tao Te Ching: “A journey of a thousand miles begins with a single step” (or “A journey of a thousand li begins with a single step”).
 
Relating this sentiment in idiom to scientific observation, the notion that large-scale phenomena may be affected by tiny initial incidents is the essence of chaos theory. However, in all the examples above, the result of the tiny initial incident is supposed to be predictable, unlike in chaos theory.
 
Subject: Re: “slippery slope”
From: Geoffrey Nunberg <[log in to unmask]>
Reply-To: American Dialect Society <[log in to unmask]>

Date: Fri, 27 Jun 2003 16:16:25 -0700
Content-Type: text/plain
Parts/Attachments:  text/plain (115 lines)
 
It struck me that “slippery slope” does a lot of the work that
“letting the camel’s nose into the tent” used to do. The earliest
cite for that one in Making of America is from 1860 (but surely it
goes back much further)—this is delightful enough to quote in its
entirety:
 
Sigourney, L. H. (Lydia Howard), 1791-1865, Gleanings,1860.
AN ARAB FABLE
 
Once in his shop a workman wrought
With languid hand, and listless thought,
When through the open window’s space
Behold!-a Camel thrust his face.
“My nose is cold,” he meekly cried,
“Oh, let me warm it by thy side.”
Since no denial word was said,
In came the nose,- in came the head,
As sure as sermon follows text
The long, excursive neck came next,
And then, as falls the threatening storm
In leap’d the whole ungainly form
 
Aghast the owner gazed around,
And on the rude invader frown’d,
Convinc’d as closer still he prest,
There was no room for such a guest,
Yet more astonish’d, heard him say,
“If incommoded, go your way,
For in this place I choose to stay.”
Oh, youthful hearts, to gladness born,
Treat not this Arab lore with scorn.
To evil habit’s earliest wile
Lend neither ear, nor glance, nor smile,
Choke the dark fountain ere it flows,
Nor even admit the Camel’s Nose.*
 
* To illustrate the danger of the first approach of evil habit, the
Arabs have a
proverb, “Beware of the Camel’s nose.”
 
A more straightforward use, also not without its charms, is found in
Spurgeon, C. H. (Charles Haddon), 1834-1892,  Feathers for arrows;
or, Illustrations from my note book. [1870]
 
WHEN a sin is let in as a suppliant, it remains in as a
tyrant. The Arabs have a fable of a miller who one day was
startled by a camel’s nose thrust in the window of the room
where he was sleeping. ” It is very cold outside,” said the
camel, ” I only want to get my nose in.” The nose was let
in, then the neck, and finally the whole body. Presently the
miller began to be extremely inconvenienced at the ungainly
companion he had obtained in a room certainly not big enough
for both. “If you are inconvenienced you may leave,” said
the camel; ” as for myself, I shall stay where I am.” There
are many such camels knocking at the human heart. Take,
for instance, compliance with a single worldly custom-dancing.
First, the custom creeps humbly to the door of the heart,
and says, “Let me in; what am I but putting one foot
before another? certainly you do not object to music, and I
would not for the world have a full band.” So in comes the
nose of the camel, and it is not long before the entire body
follows. The Christian then finds his heart occupied in full
figure by the very vice which a little while before peeped in
so meekly. ” Being up,” it says to him, ” all night at a ball,
with the eyes dazzled by lights, and the ears stunned with a f
ull band, interferes, you say, with your private devotions.
So it does. But your private devotions will have to go, for I
will not.”