From Sanford Meisner on Acting:

“Duse played in a play called Magda. There’s a scene in the last act. When she’s a young girl she has an affair with a guy from the same village, and she has a child by him. Twenty-five years later, or thereabouts, she comes back to visit her family who live in this town, and her ex-lover comes to call on her. She accepts his flowers-I got this from Shaw-and they sit and talk. All of a sudden she realizes she’s blushing, and it gets so bad that she drops her had and hides her face in embarrassment. Now that’s a piece of realistic acting! And Shaw confesses to a certain professional curiosity as to whether it happens every time she plays that part. It doesn’t. But that blush is the epitome of living truthfully under imaginary circumstances, which is my definition of good acting. That blush came out of her. She was a genius!”

-Sanford Meisner