[The] personal theme of The Blue Angel foreshadows an impending social disaster. Sadism was about to be unleashed in mass form in Germany and the film is, of course, a study of the spiritual torture and humiliation of a small-town man with whom everyone can readily identify himself. (p. 49)
[From the outset], the professor is haunted by the figure of the clown in the background, for he, the man of ideals, is himself a clown in the world of The Blue Angel. Thus at the beginning, when the professor first enters, the cabaret is shown as chaotic, almost surrealistic, with its whirling clouds, miasmic veils, and shifting backdrops; at the end, when he is part of it, it is steady, and brutal in its clarity. Everything connected with the professor suggests this interpretation—his favorite pupil called Angst, the mitigation of his masculine nose blowing after meeting Lola Lola, the very nickname Unrath (or excrement), which was later given to the Jews.
Sex and sadism, individual and social, are the main themes of The Blue Angel…. The dead bird which, in almost the first words of the film, the professor is told will never sing again, is nevertheless singing again in Lola Lola's boudoir, and sings in the last shot of all in the person of Lola Lola herself. Then for an instant the twelve apostles, in agonized poses of broken stone, file around the great Hamburg church clock, and finally Marlene herself sings the lines which sum up the film—when a man burns in lust, who can find him salvation? (pp. 50-1)
But sexual tension carries its corollaries of nostalgia and despair. Ecstasy, by its very nature, cannot endure. Slowly, in contrast to the cabaret scenes, the camera travels back down the empty classroom when [the professor] is about to leave it for good. In this last lingering embrace, as it were, the scene tenderly dramatizes the protagonist's loneliness and nostalgia for his past life which, banal though it was, had the irrecoverable gift of innocence. Lola herself, in the final analysis, is not wholly evil; as the mad professor grips her by the throat she asks him what he wants of her. (p. 51)
Nevertheless, it can be said that the whole of the dramatic construction of The Blue Angel, like its photographic composition, is centered on the sex of Lola Lola. All the scenes, the very intrigue of the film itself, radiate from this, have this as their focal point. Thus there is maintained a natural and harmonious thematic balance which makes the presentation logical and inevitable, and infinitely more gripping than the hypocritical eroticism of later Hollywood productions by the same director. Von Stemberg created his atmosphere with an almost suffocating eroticism of costume to offset cabaret scenes which are, contrary to general opinion, apt to be highly antierotic on the screen; sexiness frequently wages war with eroticism. (pp. 51-2)
Geoffrey Wagner, "'The Blue Angel': A Reconsideration," in The Quarterly of Film, Radio, and Television (copyright, 1951, copyright renewed © 1979, by The Regents of the University of California; reprinted by permission of the University of California Press), Vol. VI, No. 1, Fall, 1951, pp. 48-53.