To build castles in the air is to dream up grand plans or ambitions that have little or no chance of ever becoming real. It describes a desire, scheme or daydream that exists only in the imagination, something elaborate and appealing but built on nothing solid. The phrase is most often used to gently mock overreaching ambition or wishful thinking, though it can also describe harmless daydreaming about a future that is never likely to arrive.
What’s the origin of the phrase ‘building castles in the air’?
The image of an imaginary, unattainable castle is older than the ‘in the air’ wording. A related version, castles in Spain, from the French châteaux en Espagne, turns up in the Roman de la Rose in the 13th century and was translated into English by around 1365. Spain in this phrase represented a distant, unconquered land, so a castle built there was a castle that would never actually be held. The ‘in the air’ form of the idiom is younger, emerging in English in the late 1500s, and both versions carry the same underlying sense of forming projects that can never be attained.
The earliest known user of the English phrase is the translator William Painter, in his 1566 collection of continental tales, The Palace of Pleasure. Since the book is a collection of translated stories rather than Painter’s own invention, he may have been adapting a phrase already current on the continent rather than coining it himself. One source gives the exact wording attributed to him as describing a character “building of Castels in the ayre, fantasying a thousand deuises in his minde,” though this precise quotation has not been confirmed in a stronger source, even though Painter’s role as an early user of the phrase is corroborated elsewhere.
Not every writer has used the phrase to mean foolish fantasy. Henry David Thoreau, in Walden (1854), gave it an unusually positive twist, writing that “if you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them.” For Thoreau the castle in the air was not a mistake to be mocked but a worthy vision that simply needed practical support beneath it, a notably more encouraging reading of an idiom usually reserved for idle dreams.