ONE OF THE legends that has grown out of the life of the Spanish painter Francisco Goya y Lucientes has a servant asking him: "Why do you paint these barbarities that men commit?" To this Goya answered: "To tell men forever that they should not be barbarians."

The story is apocryphal, but it captures the spirit and philosophy of the man honored by the Boston Museum of Fine Arts in its current exhibition, The Changing Image: Prints by Francisco Goya. For Goya was molded by the age of Rousseau and Voltaire and the French Revolution--The Age of Reason. For Goya, as well as for his contemporaries, a belief in human reason was the answer to an age of corrupt religion, incompetent monarchy and political turmoil. If Goya's portraits, commissioned as they were by the Spanish aristocracy, show only a glimmer of his belief in man as the measure of all things, the etchings he made as an independent artist need no such subtlety.

It is these etchings that the Museum's show explores. Four series of his prints comprise most of the show: Tauromaquia (The Art of Bullfighting), and Disparates (Follies--published after Goya's death in 1828), the Caprichos and the Desastres de la Guerra. These last two, especially, complement each other, echoing Goya's experiences in Spanish society, his understanding of the irrational forces that make reason so difficult to express, and his conviction that reason is the only answer to these forces.

Goya began the Caprichos in 1797, at the end of a bitter love affair with the libidinous Duchess of Alba. In a good position, therefore, to cast a critical eye on Spanish aristocratic society, he conceived a series of "suenos," or dreams. For his frontispiece, he made a print which he called "El Sueno de la Razon Produce Monstruous"--the Sleep of Reason Produces Monsters. A man lies crumpled on his desk, asleep, and devoid of reason: he is attacked by a horde of owls--the Spanish symbol for dirt and stupidity--black bats and a glaring cat.

Goya, in the 80 prints that follow--most of which are in the MFA show--has depicted every evil, depraved and grotesque instinct of his society. An old woman says a rosary over a whore primping to ply her trade. A well-dressed, aristocratic woman steels teeth from a swinging corpse for use in a love potion. A group of desolate-looking monks sit drinking around a table--to this group, Goya has given a double-entendre title: "Estan Calientes" which means both "they're hot" and "they are in heat."

The ambiguity of such titles kept Goya from the clutches of the Spanish Inquisition, but the Caprichos attacked too many segments of society and its sale was a dismal failure. Goya, however, did not mean for the Caprichos merely to antagonize. He removed "El Seuno de la Razon," from its frontispiece and substituted a self-portrait: Goya as a lordly man removed from the depravity of his peers. He has been enlighted by "la Razon," and it is his duty as an artist to educate people, to bring them truth.

Goya's skill as a graphic artist was supreme--second only to his vivid imagination. He used an etched line and aquatint--a way of treating a plate with a grainy gum that results in variations in shade. With light and shade he highlights the horror of a hanged man's eyes or the sleazy expression of a prostitute's lips.

IF GOYA'S CAPRICHOS expressed the vacuity of life without reason, his Desastres de la Guerra brought out the impossibility of life without reason. The most piercing and disturbing part of the MFA's exhibition is the room devoted to the Desastres. Built on Goya's own experience during the six-year war between Spain and Napoleon's France, the Desastres show the carnage, the stench--the actuality of war. Goya shows no heroes and no villains. No supernatural forces are at work here--the agony and suffering are inflicted by people onto other people, and no one is spared.

Three prints--which Goya titles simply, "No Quieren" (They Don't Want To), "Tampoco" (Nor Those), and "Ni Por Esas" (Neither Do These)--show the brutality with which the victorious French raped the Spanish women. Figures in the shadows only hint at the viciousness, but an arc of Goya's light illuminates a half-naked woman being dragged by a French soldier away from the body of her screaming child.

Goya shows that the civilians suffered in many ways: in "Para Eso Habeis Nacido" (This Is What You Were Born For), a man vomits on a pile of typhoid-ridden corpses, against a background of mottled, dark blotches. In "Enterrary Callar" (Bury Them and Be Quiet), Goya shows a mound of bodies, topped by a weeping woman and a man covering his mouth at the sheer horror of the smell. "When the French entered the city," reports an 18th century English journalist (quoted in the excellent catalogue by Eleanor Sayre) "6000 bodies were lying in the streets and trenches, or piled in heaps before the churches." There was no longer any room in the cemeteries--bodies were flung into huge pits. Goya depicts this scene and gives it the title "Caridad" (Charity).

Even the dead are not left in peace. In "Que Hai Que Hacer Mas?" (What More Can Be Done?), five French soldiers brutally castrate a Spanish corpse.

The horror of scene after scene is too much to be endured, for Goya uses man as the measure of every single, brutal atrocity, and grinds the agony into the viewer.

This show has brought together prints from Boston, Madrid, Paris, Berlin and London to form the most comprehensive Goya show ever seen in America. It is impressive just to see the Disparates and the Desastres de la Guerra in Goya's working proofs, for these two series were published after his death, and the formal prints have been altered from what Goya meant them to be. But to have these juxtaposed with the Caprichos, and to see how Goya changed his images of human folly over 19 years is an unforgettable experience.

I wonder if Goya's faith in reason endured the Spanish-French war, which ended in 1813. For the question of his time was a gnawing fear that greed and lust might indeed win out over the pull of rational thought. For as Goya's contemporary, Alexander Pope, once asked:

With terrors round, can reason hold her throne, Despite the known, nor tremble at the unknown?