Z Evan’s review published on Letterboxd:
this will take many more viewings to fully unpack...
the images of the mirror are the most beautiful I've ever seen in a film. Maria/Natalia levitating above her bed, a cracked ceiling dripping rainwater and plaster, and a deep green Russian field trembling in waves in the wind become totally unforgettable, and the entire film sticks in your head and plays like a lucid dream.
I spent too much time the first viewing, unfortunately, trying to follow who was who and figuring out that a lot of the characters (with different names each scene) are just played by the same actors. even while trying to piece together the non-linear, stream-of-consciousness "plotline" the film left such a profound effect on me. from the very beginning scene, the mirror can give you chills all over your body the way no other work of art can.
Tarkovsky completely throws away any conventional elements of story and plot structure, which makes the film much more of a task to fully dissect. but it is only obtuse and convoluted because it is meant to be; a collection of half-memories half-dreams half-newsreel-reality with subconscious and symbolic connection that add to a greater whole.
all of the classic tarkovsky images are here: water, (I think means the passage of time and it's cyclic continuum) milk (purity? motherhood? religion? both?) and a repeated theme essential to many Tarkovsky and generally well-regarded filmmakers' oeuvres. the classical elements—earth, wind, fire, water (a theory developed like the dragon all over the world simultaneously, from Buddhism to ancient Hellenistic Greece)—play an important part in the mirror, showing the physical and metaphysical makeup of the world as fundamentally these four elements. there is painstaking realism in Tarkovsky, sure, but most of his wonder is in the ability of his to fully portray the actual symbolic and spiritual weight that nature and the world has on humans. there is no part of Tarkovsky that is cynical or believing that flesh and blood, dirt and soil, are the only things to possibly extrapolate from the experience of life. he rejects postmodernist and existentialist posturing that "this is all there is" and "we create meaning for ourselves"and "god is dead"; to him, everything has an objective and subjective meaning in the world, and every tangible object holds two levels of literal and non-literal weight that are equally as valid and felt.
along that line, I think that the mirror is meant to be understood...to a point. beyond knowing which character is onscreen, and when scenes take place in relation to each other, all other understanding is left to the audience. this is tarkovsky's swan song to all of us: his ultimate gift is this brilliant and magical puzzle of a thousand small pieces that adds up to something different with each time, each person placing them together. these symbols and images are universally resonant and understood, and up to us is the impossible task of figuring out why. this is the meaning of art, posing with the questions with answers that we cannot articulate, but we know and feel in our heart of hearts.