Peter Schjeldahl at The New Yorker:
The chromatic subtleties contribute to an unsettled feeling. A more substantial jolt occurs when you register an over-all spatial distortion: the forms stretch horizontally, so that the length of Anna’s concealed legs, angled and descending to an upholstered footstool, suggests the anatomy of an N.B.A. draft pick. The more you notice of the composition’s economies—such as the cavalier indication of the bentwood chair legs, at the lower right, and, at the lower left, three perfunctory diagonal strokes that do for establishing the plane of the floor—the more happily manipulated you may feel, in ways that, like the camera tricks of a great movie director, excite a sense of the scene as truer to life than truth itself. It took me an hour of inspection to take in an inconspicuous, brownish strip across the bottom of the canvas. Anna’s dress falls smoothly past it and out of the picture. It is the edge of a stage or a platform. Whistler is looking up at his mom.
“Yes, one does like to make one’s mummy just as nice as possible,” Whistler allowed years later, answering friends who praised the speaking likeness of the portrayal. But he was exasperated by sentimental responses to the work. He regularly preached that subject matter should be regarded merely as a pretext for adventures in aestheticism. He said, “To me it is interesting as a picture of my mother; but what can or ought the public to care about the identity of the portrait?”