"Glass... helped to alter the very concept of self. In a small way, glass had been used for mirrors by the Romans; but the background was a dark one, and the image was no more plain than... the polished metal surface. By the sixteenth century, even before the invention of plate glass that followed a hundred years later, the mechanical surface of the glass had been improved to such an extent that, by coating it with a silver amalgam, an excellent mirror could be created. ...For perhaps the first time, except for reflections in the water and in the dull surfaces of metal mirrors, it was possible to find an image that corresponded accurately to what others saw. ...The use of the mirror signalled the beginning of introspective biography in the modern style... 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... 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, slyness, covetousness, weakness... quite as clearly as health, 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... 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."