David Thomson in The Independent:
In his autobiography, The Words (1964), Jean-Paul Sartre described his discovery of cinema as a child. He would have been 10 years old in 1915 when The Birth of a Nation opened. But he hardly noticed particular films at first. What he saw or felt was something he called “the frenzy on the wall”. That could have been a reaction to the brilliant battle scenes in Griffith's films, but it also covers the still face of Garbo absorbing romantic loss, or the stoic blankness of Buster Keaton baffled by the physical chaos around him. The frenzy was in the whirl with which projected film ran at 16 or 24 frames a second, a passage of time that seethed on the wall – and, paradoxically, the serenity of another reality. That was the inherent madness and the magic in cinema: that we watch the battle but never risk hurt, and spy on Garbo without having her notice us.
At first, the magic was overwhelming: in 1895, the first audiences for the Lumière brothers' films feared that an approaching steam engine was going to come out of the screen and hit them. That gullibility passed off like morning mist, though observing the shower in Psycho (1960) we still seem to feel the impact of the knife. That scene is very frightening, but we know we're not supposed to get up and rescue Janet Leigh. In a similar way, we can watch the surreal imagery of the devastation at Fukushima, or wherever, and whisper to ourselves that it's terrible and tragic, but not happening to us.
More here.