When you leap in the dark it means that you are doing something without being sure what the end result will or might be.
Author John E. Ferling wrote a book entitled, ”A Leap In The Dark: The Struggle To Create The American Republic” that was published by Oxford University Press in 2003. The book paints “a brilliant portrait of the American Revolution, one that is compelling in its prose, fascinating in its details and provocative in its fresh interpretations.”
Likewise, author James M. Skinner of the Department of History at Brandon University in Manitoba (Canada) wrote an article for the Manitoba Historical Society for their Spring 1993 magazine entitled, “A Leap in the Dark: The Transition from Film Censorship to Classification in Manitoba, 1970 – 1972.” The article dealt with the Manitoba Film Censor Board which was established in 1923 under the Amusements Acts and the changes that came about with its reformation in 1972.
Edward Stanley, the 14th Earl of Derby, served as Prime Minister in England no less than three times: 23 February to 17 December 1852; 20 February 1858 to 1 June 1859; and 28 June 1866 to 25 February 1868. In February 1867, Disraeli introduced his Reform Bill months after Edward Stanley formed his third ministry on the resignation of Lord John Russell. Edward Stanley returned to Disraeli’s original proposals when the Commons found Members of Parliament demanding a more radical measure. The legislation was passed on 9 August 1867. In his speech, following the third reading of the Bill in the House of Lords, Edward Stanley said:
No doubt we are making a great experiment and taking a leap in the dark but I have the greatest confidence in the sound sense of my fellow-countrymen, and I entertain a strong hope that the extended franchise which we are now conferring upon them will be the means of placing the institutions of this country on a firmer basis, and that the passing of this measure will tend to increase the loyalty and contentment of a great proportion of Her Majesty’s subjects.
Charles Morley, in the introduction to his book “Elements of Animal Magnetism” published in 1841 wrote:
In 1784 this Academy appointed a committee from their number to examine and report on animal magnetism; but instead of confining their attention to the facts which were laid before them, they sought the cause by which they were produced, and inquired into the existence of the fluid described by [Franz Anton] Mesmer, but it escaped their research. They could not see, taste, or touch it; they could not collect it in masses, and could neither measure or weigh it; therefore they made a leap in the dark, and concluded that animal magnetism did not exist.
On December 3, 1787, the Connecticut Courant and Weekly Intelligencer newspaper published in Hartford, CT ran a Letter to the Editor that began, “It is unhappy both for Mr. Gerry and the public that he was not more explicit in publishing his doubts.” The author, known only as “A Landholder” wrote:
In terms of art, which we often find in political to the honourable gentleman, it might have appeared more definite and ambiguous but to the great body of the people altogether and to accept it they must leap in the dark.
In 1675, Thomas Hobbes moved to Derbyshire to spend time with his friend, the 3rd Earl of Devonshire. Four years later, Thomas Hobbes suffered a fatal stroke while working on yet another book. His last words were recorded as being:
I am about to take my last voyage, a great leap in the dark.
Idiomation was unable to find an earlier published or recorded version of this expression and with that, the honour of being the originator of the phrase goes to Thomas Hobbes in 1679.