Where the goals in Chaplin's films are social, physical, and explicit, those in Keaton's are metaphysical and implicit. Chaplin's art is rooted in a period which could believe in social solutions, while, for Keaton, there are no solutions—or rather, the solutions, like the problems, lie somewhere just outside the frameline, somewhere beyond the film's conclusion. His films, unlike Chaplin's, end happily, his ambitions and those of his girl meeting finally at one point. But these endings suggest a temporary adjustment of ultimate divergences; any solutions fate may provide for this man are essentially irrelevant. One critic has spoken of "the admirable play of horizontals and verticals" in his films; the fundamental disparity between Keaton's line and that of the other characters is final and immutable. Keaton is willing to join in the game, a game not entirely innocent, in which the stakes may be life and death—but it is not his game, and one senses that, for him, all has already been lost.
Keaton moves in a windless vacuum of his own, his directions suggesting the trajectory of a bullet moving through a wind tunnel, buffeted by whirlwinds of ceaseless violence. His lack of engagement extends to his audiences as well, from whom he has always seemed separated as if by a glass and soundproof wall. His lack of emotional response, his endlessly rigid and inflexible behavior imply a previous hurt which even he cannot remember, but which controls his every movement. The dignity and silence of Keaton's suffering speak, as do Garbo's, of an immensity of early sorrow which cannot be put into words. There is in his films always something withheld, a little turned away from the audience, the nature of which is open to conjecture. It is this quality of reserve which in the end makes his performances so powerful. (p. 14)
Christopher Bishop, "The Great Stone Face," in Film Quarterly (copyright 1958 by The Regents of the University of California; reprinted by permission of the University of California Press), Vol. XII, No. 1, Fall, 1958, pp. 10-15.