The four great operas of Mozart all show paradigmatically how strongly music can mould dramatic form. The Magic Flute and The Marriage of Figaro show further how such dramatic form can articulate a consistent, profound action. In these masterpieces, all of Mozart's eloquence and strength, his faultless response to action, his control over the dramaturgical wealth of the ensemble, his sensitivity to character in the aria, his famous ingenuity, sympathy, delicacy, and humor, his superb sense of artistic form on every level — all this is fired to cast a single dramatic conception. One cannot very well describe such a conception without lapsing into platitudes; one can find words more easily for operas like Don Giovanni and Cosi fan tutte, wherein the dramatic ideas are half-formed or unresolved despite very great beauties. But where the dramatist has been successful, the idea cannot be defined except as the work itself. The meaning of a complete work of art will be manifested only in the medium that realizes, consummates, or creates it. The vindication of opera as drama comes in such occasional, unique triumphs; and among these, Mozart has left our most precious examples.
—Joseph Kerman, Opera as Drama, 1988, University of California Press
On the evidence of the Da Ponte operas and Die Zauberflöte, Mozart is one of those rare creative beings who comes to disturb the sleep of the world. He was put on earth, it seems, not merely to provide an anodyne to sorrow and an antidote to loss, but to trouble our rest, to remind us that all is not well, that neither the center nor the perimeter can hold, that things are not what they seem to be, that masquerade and reality may well be interchangeable, that love is frail, life transient, faith unstable. [...] Mozart's [dramatic] universe is itself uncertain, a maze of doorways to the unknown and the unexpected. Everywhere there are dislocations, fissures, tears, and weak spots; cynicism and disillusionment ... permeate his resolutions, corrupt his happy endings. [...] For [Mozart], the beneficence of the Creation was not self-evident, or, at least, it was necessary to reconcile it with the stations of the Cross. Tranquility must be earned, not ratified or colluded in. Evil persists even after the music has had its say.
—Maynard Solomon, Mozart: A Life, 1995, HarperCollins Publishers
Mozart's influence transcends history. Each generation see something different in his work. [...] Mozart's music, which to so many of his contemporaries still seemed to have the brittleness of clay, has long since been transformed into gold, gleaming in the light, though it takes on a different luster for each new generation. Without it each generation would be infinitely poorer. No earthly remains of Mozart survived save a few wretched portraits, no two of which are alike; the fact that all the reproductions of his death-mask, which would have shown him as he really was, have crumbled to bits seems symbolic. It is as though the world-spirit wished to show that here is pure sound, conforming to a weightless cosmos, triumphant over all chaotic earthliness, spirit of the world-spirit.
—Alfred Einstein, Mozart: His Character, His Work, 1945, Oxford University Press