When the old armoire in the cluttered storeroom of the austere Mexican convent is thrown open and its treasure trove of papers fly out, it is like rays of sunshine penetrating a dark, suffocating miasma of gloom and oppression.

When the old armoire in the cluttered storeroom of the austere Mexican convent is thrown open and its treasure trove of papers fly out, it is like rays of sunshine penetrating a dark, suffocating miasma of gloom and oppression.

That moment of wonder and joy is the key to "The Tenth Muse," Tanya Saracho's vibrant play about the liberating effect of the writings of Sor Juana Inés de la Cruz on three young women who are cloistered not only in a convent but by the racial and intellectual restrictions of their time.

The work, beautifully directed by Laurie Woolery, had its world premiere in the Oregon Shakespeare Festival's Bowmer Theatre on Saturday.

Sor Juana was a 17th-century Mexican nun, widely admired for her poetry, plays and social commentary, who was silenced by the Inquisition. OSF originally commissioned Saracho to adapt Sor Juana's classic romantic farce, "The House of Desires," as part of the festival's program of presenting world classics from other times and cultures to OSF audiences.

But Saracho soon realized that what made "The House of Desires" unique was Sor Juana's story. Colonial Mexico existed under a rigid racial caste system. At the top were the peninsulares, those born in Spain who emigrated to Mexico. Directly below them were the criollos, Mexican-born but of full Spanish descent. And below them, held in contempt, was the large majority of the population, of indigenous Indian or mixed-race descent, called mestizos.

The percentage of European blood determined everything, from occupations to marriage partners to levels of taxation.

But whatever her caste, a single woman was vulnerable. Full Spanish-blooded women without a husband, whether peninsulares or criollas, frequently entered the safety of convents and took their vows as nuns. Women of lower caste were often given to convents as servants to keep them out of harm's way.

Because the nuns came from wealthy and powerful families — bringing a large dowry and continued family support with them — the convents of the capital, Mexico City, were not always strictly cloistered. The women, used to a lively intellectual and social life, often hosted poetry readings or theater performances in their public rooms, attended by men and women from outside the convent.

Periodically, the stern eye of the Spanish Inquisition landed on Mexico. Intellectuals, converted Jews accused of insufficient Christian zeal and the liberal ways of some religions were forcibly brought to heel. In 1690, Sor Juana was caught in one of these purges and was forced to renounce her writings or face burning at the stake. To protect others in her convent, she recanted and her work was burned.

"The Tenth Muse" opens 20 years after Sor Juana's death in her convent. Three young women arrive to join the community, but not as nuns. Manuela (Alejandra Escalante), a criolla, has been sent there by her family to wait out an unfortunate out-of-wedlock pregnancy. Jesusa (Vivia Font), an educated mestiza (half-Spanish, half-Indian), has been sent by her more liberal convent to be a caretaker to a mentally unbalanced criolla nun named Sor Isabel (Sofia Jean Gomez) — Sor Juana's niece. Tomasita (Sabina Zuniga Varela), a Nahua Indian, has been given to the convent by her mission to work as a kitchen maid.

The head of the Inquisition, the archbishop, is about to visit and the atmosphere is tense. The Mother Superior (Judith-Marie Bergan), a peninsulare, has kept the Inquisition at bay since the convent came under scrutiny along with Sor Juana by enforcing a rigid religious rule. The convent lives in fear of her, from her second in command, Sor Rufina (Vilma Silva), to the convent's freewheeling cook, Sor Filomena (K.T. Vogt). Only Sor Isabel, nearly blind and mentally fragile, openly rebels against the Mother Superior's intimidation.

When the three new arrivals, relegated to an unused basement storage room as a dormitory, find those papers — rescued writings of Sor Juana — and begin to act out Sor Juana's play, rigid gender and caste roles are turned upside down. Their lives and the precarious discipline of the convent are irrevocably changed.

With scenic design by Richard L. Hay, lighting by Jane Cox, costumes by Christopher Acebo and haunting music by Rodolfo Ortega, this production fulfills Woolery's hope "to conjure Sor Juana's spirit." The vivid evocation of time and place also shows the sure hands of dramaturgs Luis Alfaro and Lue Morgan Douthit.

Of course, Saracho's depiction of the period's brutal racism and intellectual rigidity — power, respect, even common decency are determined by the color of one's skin — resonates to our time and current events. In this moment, when casual racism and gender discrimination are re-emerging as legitimate and even respectable political positions, "The Tenth Muse" reminds us that Sor Juana's struggle — even at the risk of personal peril — needs to continue.

"The Tenth Muse" runs through Nov. 2. For tickets, visit www.osfashland.org or call the box office at 541-482-4331.

Roberta Kent is a freelance writer living in Ashland. Reach her at rbkent@mind.net.