If our eyes are the windows of our soul, then wearing sunglasses is like putting up the shutters. Try gazing into the eyes of your loved one with a pair of Ray Bans perched on your nose. See, it just isn't the same.
Shady characters can have a hidden agenda for cutting off lines of communication with a pair of dark lenses. The Chilean dictator, Augusto Pinochet, admitted in a biography published last year that he took to wearing sunglasses after his 1973 coup to mask his mendacity: "Lies are discovered through the eyes and I lied often."
In fact most of us have an ulterior motive for sporting sunglasses. It's not just that they protect our eyes - shades are cool. And stars of stage, screen and sports often shape the latest trends.
Sales of metal-rimmed aviators - first made popular by American airforce pilots - took off after Tom Cruise wore them in Top Gun, and without their eyewear the gang in Reservoir Dogs would have looked like more like Mormons than murderers. Hi-tech wraparounds designed for cyclists and skiers are now common on the cricket field, tennis court andgolf course.
Some people are synonymous with sunglasses style. It's hard to imagine Kojak or Carlos the Jackal, Michael Jackson or Jackie O, Roy Orbison or Bono without their ever-present accessories. If you're a celebrity living in the glare of publicity, they help to disguise last night's excesses, deflect the paparazzi's flash guns and make you more impenetrable.
Before sunglasses became the essential summer accessory, most people would wear a hat to keep harmful ultra violet rays out of their eyes. But tinted eyeglasses date back to the 1750s when eyeglass maker James Ayscough recommended the calming effects of blue or green tinted lenses. The Roman emperor Nero reputedly held an emerald up to his eye as he watched gladiators fight, and the Egyptians and Chinese were said to have cut coloured rock crystal to protect their eyes. But the original sunglasses were made by Arctic-dwelling Inuits. They wore pieces of whale bone with slits to see through to avoid snow blindness and block out the dazzling whiteness of their spectacular surroundings.