The glass mirror, which began to be widely produced in the 16th century, tends to be characterized as a tool of self-love: one gazes at the image in the glass as Narcissus gazed at the reflection in the water. But, as Lewis Mumford suggests in his 1934 masterwork  Technics and Civilization, the mirror is better characterized as a tool of self-loathing:

The self in the mirror corresponds to the physical world that was brought to light by natural science in the same epoch: it was the self in abstracto, only part of the real self, the part that one can divorce from the background of nature and the influential presence of other men. But there is a value in this mirror personality that more naive cultures did not possess. If the image one sees in the mirror is abstract, it is not ideal or mythical: the more accurate the physical instrument, the more sufficient the light on it, the more relentlessly does it show the effects of age, disease, disappointment, frustration, slyness, covetousness, weakness — these come out quite as clearly as health and joy and confidence. Indeed, when one is completely whole and at one with the world one does not need the mirror: it is in the period of psychic disintegration that the individual personality turns to the lonely image to see what in fact is there and what he can hold on to; and it was in the period of cultural disintegration that men began to hold the mirror up to outer nature.

It is the vanity of neuroticism more than the vanity of narcissism that the mirror encourages.

Social networks like Facebook are also reflective media, but the image of us that they return, insistently, is very different from the one presented by the glass. What’s reflected by the network is not the part of the self “that one can divorce from … the influential presence of other men.” Rather, it is the part of the self that one cannot divorce from the social milieu. It is, in that sense, more “mythical” than physical. We project an idealized version of the self, formed for social consumption, and the reflection we receive, continually updated, reveals how the image was actually interpreted by society. We can then adjust the projection in response to the reflection, in hopes of bringing the reflection closer to the projected ideal. And so it goes. The “influential presence of other men” becomes inescapable. It is there, tangibly so, even when we are alone. The image reflected in the screen remains a lonely image, but it reflects not outer nature but outer society: the light of others’ eyes.

What we see in the mirror may be, literally and figuratively, dispiriting, but at least it sets us on firm ground. The glass can be monomaniacally cruel, but it is always monomaniacally fair. The screen’s disintegration of the self is more insidious, if only because what’s reflected never precisely matches what’s projected. There’s nothing to “hold on to,” in Mumford’s words. There’s nothing “there.”