According to the Christian teachings vanity is
Presenting yourself as attractive to gain attention from a partner is a fundamental element to our species, to our survival to continue populating. In nature the male Bowerbird builds elaborate structures out of feathers and twigs, the male frog sings, the peacock displays a large colourful tail, all with the aim to attract a mate. It's inbuilt within the genetic fabric of us, to let it consume you would result in sin according to Christianity, but to deny vanity completely would go against our nature. As humans in an image conscious society the mirror becomes our essential tool.
It's conceivable that for thousands of years long before the actual invention of a mirror our ancestors would have been gazing at their reflections in still pools of water, but to pin point the existence of an actual mirror we go back 2,400 years where it is believed the first mirror-makers lived near the city of Sidon in Syria. Glass itself was invented in neighbouring Lebanon so it makes sense the mirror would be nearby. Through a process of blowing a thin sphere of glass into a bubble and pouring hot lead into the bulb of the glass, once cooled it would coat the inside of the glass which could then be broken into pieces. These pieces were much clearer than polished copper or bronze, and the new technology would spread rapidly throughout the Roman Empire. Useful of course for their self-admiration, but also the beginning of mirrors appearing in design as they would start to utilize it to create magical amulets.
Once embraced by the Roman's the mirror would take its next step forward between the 12th and 17th Century. As they altered the making process slightly to give the mirror a thin metal backing it would give it much more freedom to be further incorporated into objects and as furniture. Observing and acknowledging change can be a beautiful process. From pools of water to broken shards of glass to the immense mirrored furniture and structures we know today, gradual but staggering change and evolution over time. The ability to observe is one of the great gifts of a mirror, to visually see your own change and appearance at its best and worst. From your intrigue and innocence as a child to the eventual wrinkled eyes that have seen it all, it's all reflected back at you.
Venice would be one of the first locations where successfully experimenting with mirrored furniture pieces would take place, so much so that to this day Venetian furniture is still one of the most popular. Their creativity and ingenuity would produce fantastic pieces encompassing floral etching and unique patterns all heavily influenced by the art-deco movement. Venice at this time became the Mecca of mirrored furniture but gradually over the following centuries many left, taking their ideas with them to France and England and the rest of Europe.
By the 19th Century cheaper techniques in mirror production led to a great proliferation in their use. No longer limited to being incorporated in just furniture and wardrobes extensive use began to take place in grand decorative schemes and public places. With this a new benefit to the mirror and reflective surface would unfold, a creation of space. The ability to create an illusion that there is more is one of the key subtle features we discover with mirrors in design.
With all the inventions that we take for granted today based around the use of mirrors; microscopes, telescopes, cars, iPhone's, HDTV's... all of it came from that initial intrigue in our reflection. Pursuing our vanity and our natural desire to look our best and see how we appear, to follow that basic impulse too far would I agree be a path to sin. The mirror however is one of the few hopeful examples of human's ability as a collective to progress from the initial basic instinct, move past it and see the greater bigger picture of discovery, curiosity and reflection.