A skyhook is a "hook" used to lift an object on a long cable hanging from the sky, without readily-apparent support. In the mid-20th century it was common in the Boy Scouts

Boy Scouts of America

The Boy Scouts of America is one of the largest youth organizations in the United States, with over 4.5 million youth members in its age-related divisions...

 and occupations such as oil drilling to send new recruits on a futile search for such an imaginary object, as a practical joke. The term has subsequently lent its name to some real mechanisms that use an airborne hook or hoist, and to other products or ideas that allude to the concept. The American philosopher Richard Rorty

Richard Rorty

Richard McKay Rorty was an American philosopher. He had a long and diverse academic career, including positions as Stuart Professor of Philosophy at Princeton, Kenan Professor of Humanities at the University of Virginia, and Professor of Comparative Literature at Stanford University...

uses the term to refer to a hypothetical metaphysical system that leads to a universal perspective.