''A man's home is his castle,'' castle-keep, castellated . . . of all the once-upon-a-time elements in architecture, the castle inspires the most fantasy.
Hearth, gate, cottage are nothing in our mythology compared with castle and its corollary images of dungeon, ivory tower, moat.
Military or romantic, solid or in picturesque ruins, it tenants our fancy.
If there were no castle, where would Puff the Magic Dragon, King Arthur, or the modern heroes of Ursula LeGuin find their homes and foes. Could we revisit Brideshead any place else than at Castle Howard? Or, for that matter, the Magic Kingdom?
This is the convincing thesis made in 83 exhibit pieces at the Hammond Castle Museum's show of ''Castles: An Enduring Fantasy'' in Gloucester, Mass., through April.
The exhibition reinforces the castle's millenial presence: the structure, tinted by romance, evolved as a Western symbol from Sir Walter Scott through the Gothic Revival to the White Tower Restaurant.
Beyond its own content, the show reminds us of how the battlemented, crenelated world around us - the world of turreted, flag-bearing pinnacles of commerce, of apartments and fairy-tale motels, of N.C. Wyeth and braggadocio banks - sprang from the 11th-century feudal outposts of England.
Not many locales could better serve the aims of this enterprising display than Hammond's Jazz Age castle on the Atlantic. All dimness and carved masonry, stained glass and pointed arches; spiral, stone-vaulted staircases and stone-flagged floors, it is an ideal stage set.
The museum's Great Hall, a 65-foot-high space used for organ concerts, now holds the objects of the Age of Chivalry under the feudal banners that colored that era's drama of love and war.
While the charm of the museum's ocean views and glassed courtyard conveys the drama of Hammond's 20th-century concoction of castle life, it also demonstrates its less-endearing elements. Stairways no wider than an arm's width, windows too small to let in the light we moderns like, and a certain winter chill supplement the show's glimpses of medieval life.
Hammond himself liked to emphasize this authenticity, allotting his guests a room without electricity to get the full (icy, unlit, unheated) flavor of the past.
The show gives this flavor by more conventional means.
The exhibition proceeds from a slide show and an adjacent model of Castle Harlech to segments winding in and out of the castle.
Organizer Naomi Reed Kline has tidily divided the subject into periods: the Middle Ages, the Age of Chivalry (1100 to 1500, when castles went from encampments to administrative centers of war and courtly love); the 18th and early-19th centuries, and the Gothic Revival, when their jagged silhouettes stirred the romantic spirit of the age to write and re-create them; and the mid- 19th century when ''The Popular Explosion'' came via N.C. Wyeth and Walt Disney.
Objects amplify the armchair adventurism - a purse topped with a castle, wax seals of castles giving the stamp of authority, even a panel of maps showing how cartography grew from the mapmaker's elevated view at the top of the castle tower.
Placards also detail construction methods and living places from latrines to kitchen.
Unfortunately, the show suffers from a surfeit of such words; meanwhile, it misses a chance to elaborate on the castle imagery of today's landscape in a more visual way.
Those with a background in architecture may know of Horace Walpole's castle at Strawberry Hill in the middle of the 18th century. Others get no suggestion that but for this ''toy castle,'' as one historian put it, ''we might never have witnessed the prairie-style houses of Frank Lloyd Wright, built from the inside out, or been confronted with the glass towers of Ludwig Mies van der Rohe.''
The initiate again may know that the skyscraper derived, in some sense, from the 19th century and Viollet-le-Duc's restoration of Gothic castle and cathedral. But the novice will not.
(In fact, the mock library here, a copy of St. Paul's and no castle at all, underscores a certain scholarly lapse; the show neglects to mention the Gothic church, as well as castle, as role player in the neo-Gothic revival.)
Nowadays architects attend to the past for its Roman and Renaissance background, its symmetry and classical orders in design. This show might have focused on the medieval castle, its concrete contributions along with its literary ones.
Like Viollet-le-Duc, who scorned the Renaissance to restore - or theatrically resurrect - Vezelay, Notre Dame de Paris, the entrance to Carcassonne City, and the medieval castle at Pierrefonds, our reverence for the past is selective. Like Beckmann who built the folly that collapsed at Fonthill, we need to care for all our foundations.
Since other shows have brought us classical elements, then and now, appliqued dead-center style on Beaux Arts buildings, ''Castles'' had a broader potential.
Glimpses of, say, San Simeon, William Randolph Hearst's castle on the coast of California, or photographs of castles on the Hudson to parallel the misty Hudson River School paintings would show how the castle dream crosses the Atlantic.
It would place Hammond's own castle in perspective.
A simple shot of the cloisters commissioned by the same firm that did the museum, Allen & Collins, would have added to the historic context. So would views of a Sears, Roebuck tower or a row house. Designs in collegiate gothic or franchise fairy tale are also its peers.
Instead, the innocent viewer emerges with the mistaken notion that the Gloucester edifice was more eccentric than it was.
For all that, ''Castles: an Enduring Fantasy,'' like its subject, has its enchanting elements. It reminds us of the longevity of an idea, both literary and visual, on the landscape of our minds and the settlement of our environment.
''In a few years after I am gone, all my scientific creations will be old-fashioned and forgotten,'' the electronics pioneer who built this place observed. ''Only that which meets the eye remains.''
''Hadrian and Cauis Sestus have whispered in my ear,'' he wrote.
''I want to build something in hard stone and engrave on it for posterity a name of which I am justly proud.''
The show explains how and why that pride made itself appear in castle form.