# Prologue: the Way of Purity

The purpose of a good watch is not merely to tell the time. Any cheap mechanism can tell the time.

A good watch exists

• to celebrate time;
• to celebrate the telling of time;
• to celebrate the means by which the time can be told.

There are two modes of celebration. They exist in mutual tension and harmony. We may call them the Way of Purity and the Way of Complication.

The modern Way of Complication was born in 1364 with Giovanni de’ Dondi’s Astrarium, which in addition to the time showed the position of every planet in the heavens. In mechanism, the Way of Complication celebrates intricacy, and delights in taking what seemed impossible and making it possible. In display, the Way of Complication manifests itself in subsidiary dials showing the phases of the moon, the tides, and the time of the day on Mars. At times, the primary function of actually telling the time is buried under the complications.

The ideal of the Way of Purity is to tell the time with as little mechanism and as little complexity as possible. As with the Way of Complication, the real delight is when what had seemed to be impossible turns out to be possible after all; and this is what the entire Optical Gearing project is about.

Because the universal rule is to measure the time in hours and minutes [and seconds], it seems to be necessary to have at least two [or three] visible moving parts. This is because the indications on a clock face have to move at two [or three] different speeds, but no one physical object can move at more than one speed at a time.

But this apparent limit is an illusion. Thanks to Optical Gearing, we can follow the Way of Purity all the way to its ultimate ideal, with the entire display of hours and minutes [and seconds] being accomplished by a single moving object. The object revolves once every 12 hours, but the eye, looking at it, sees the time displayed in the traditional, comprehensible way. All that is needed is a combination of advanced mathematics, optics, and accurate engineering.

Background: the Vernier Principle