Luminous is an overused word in theater criticism, but the word is aptly applied to Shirley Knight, the Tony- and Emmy-winning actress who died at age 83 on April 22 in San Marcos.


Knight’s daughter, Kaitlin Hopkins, founded the musical theater program at Texas State University. Although she maintained a residence in Los Angeles, Knight was a presence on the campus. She died of natural causes at Hopkins’ home.


A product of the Actors Studio heyday, she is linked to those method stars who may have burned brighter but probably not as consistently. There was never a part, small or star, she didn't illuminate from the inside out.


After receiving an Oscar nomination for her performance in "The Dark at the Top of the Stairs," in which she played a teenager while in her mid-20s, Knight was cast as Heavenly Finley in the 1962 film version of Tennessee Williams' "Sweet Bird of Youth," directed by Richard Brooks. Her beauty had a celestial quality that might have seemed to earn her the part. But there was more to the actress than Hollywood glamour. There were contradictions worthy of a Williams heroine. Her Heavenly combined porcelain fragility with bitter strength. The movie belonged to Geraldine Page and Paul Newman, but Knight's Heavenly clarified the drama's tragic stakes.


In his book "A Method to Their Madness: The History of the Actors Studio," Foster Hirsch captured the vital paradox that was Knight's presence: "Blonde, with dainty features and a translucent complexion, she might have become the conventional ingenue, playing a string of decorative roles. But anger churned beneath that pretty facade, and a sour expression — a stingy smile tinged with irony — promised thunder."


» RELATED: We Love This So Much: A Sondheim YouTube spiral


She was committed to the work of acting, to uncovering the grit of her characters, to revealing the sand caught in the gears of the human machinery. She played Irina on Broadway in Anton Chekhov's "The Three Sisters" alongside Kim Stanley and Page in the Actors Studio production directed by Lee Strasberg, passing up the chance to be the Ophelia opposite Richard Burton's Hamlet. Her loyalty was to the community that had inspired her.


Knight, who won a Tony in 1976 for her performance in Robert Patrick's "Kennedy's Children," was a throwback to an era when acting was upheld as a rigorous discipline of craft and soul. Her career had longevity because it was predicated not on great looks but on her searching humanity.


Age, in addition to adding to her trove of Emmys (including one for HBO docudrama "Indictment: The McMartin Trial"), opened up possibilities. Twice I saw her onstage in her later years, once in Horton Foote's "The Young Man From Atlanta," in which she was nominated for a Tony for a performance so suffused with detailed life that it was astonishing such a feat of naturalism could be pulled off with so little fuss. She understood the denial of the grieving mother she played down to the brand of hairspray stiffening her coiffure. It was a performance that transformed abstract psychology into unadulterated behavior.


Almost as impressive was the way Knight, working discreetly off-Broadway in Deborah Grimberg's largely forgettable "Cycling Past the Matterhorn," endowed a playwriting doddle with intricate layers of felt experience. When I reviewed the play for the Village Voice in 2005, I commented on Knight's gift for never revealing "more than what's needed, though always more than you'd expect."


» RELATED: Quiz: Test your Renée Zellweger knowledge


In eulogizing Knight, I can't help thinking of her eulogy for Kim Stanley. I have a copy of the email that was read at the Actors Studio in New York in October 2001, when the city was still reeling from the 9/11 terrorist attacks. During the morning of the memorial service, New York was awash in the fresh fear of an anthrax scare. I remember wondering if I should take the subway or walk the two miles uptown. I arrived on time via subway and was uplifted by Knight's words, which communicated the values to which she held fast throughout her magnificently modest career:


"I first met Kim Stanley in 1964. I was chosen by Lee Strasberg to play Irina in the Actors Studio production of Chekhov's "The Three Sisters." Imagine my excitement to discover that I was to star (in my Broadway debut) with Kim Stanley and Geraldine Page as my sisters. It would be impossible to relate how important Kim was to me in my development as an actor. I had seen her in the play about Freud and thought she gave the most extraordinary performance. One night at the beginning of the run of "The Three Sisters," Kim received applause on her exit. She came off stage muttering, "Well, that will never happen again." After the performance I asked what she meant as I assumed all applause was a good thing. She said, "Honey, if they can put their hands together, they aren't feeling (crap)." It was a revelation to me that the object as an artist was to make the audience feel and to enlighten them and that applause in the middle of a dramatic play was stopping the journey. She was always kind and loving to me as well. Another night during the run I picked up a piece of broken glass from the floor where I knew she would be kneeling. She clasped my hand and it began to bleed. She did not for a moment come out of the play but simply and lovingly placed her handkerchief on the wound. She also took me to the hospital after for stitches. Every time I look at my right palm, I am reminded of Kim. Not that I need a wound to remind me — I have the memory in my mind and heart of possibly the greatest American actress in the 20th century. With love, Shirley Knight."


Knight's performances on stage and screen have etched in our memories and hearts the example of an actor who unfailingly honored her art.


American-Statesman staff writer Michael Barnes contributed to this report.