Darkness may best be defined as the absence of visible light. This alone suggests the manner in which light, and its counterpart, always coexist. We cannot think of one without the other, and understanding the relationship between the two is the key to lighting design. As designers, we not only think in terms of the quality and quantity of light we employ, but also the degree of contrast and depth of shadow we create. We can decide to retain darkness rather than simply add light.

It is very difficult to experience absolute darkness in the natural world. There is always some presence of light, however minimal, whether it is the light from stars long extinguished, the soft ambient glow of reflected sunlight from the moon, or the omnipresence of man's impact on the planet. It is only when we deliberately create total darkness that we can fully experience the condition. But to what end? As artist James Turrell has observed, we even dream in light. Unlike many other creatures, we are not well adapted to total darkness. We are a diurnal, not a nocturnal, species. We have evolved to see in light.

If it is difficult to experience total darkness in the natural world, then it is almost impossible to escape the presence of visible light in our built environment. We live in a society that seeks to use light at every opportunity. Whether this is to help extend the day, provide safety and security, or simply enhance our lives, we employ bountiful amounts of light. Turning the lights off has become a far more conscious act than turning them on.

To that end, when we talk about darkness we are rarely referring to a total condition rather than the degree to which light is present. This leads us into the world of shadow and shade that is so familiar to artists. When learning to sketch, we are taught to prescribe a circle with a line. It only becomes a sphere when we add shade. It only exists as an object in space when it casts a shadow. The relationship between light and built form is entirely composed in this manner. Indeed, many of our references to darkness are through art, whether it is the chiaroscuro of the painter, the dramatic contrast of the theater designer, or the atmospheric design of the film director.

But there is another side to darkness. Like light, it has both a poetic and symbolic role in our society. Light and dark have significant meaning to many people in all traditions—whether it is the good versus evil of Western religion or the yin and yang of Eastern philosophy.

So like light, darkness is not just about quantity but also perception. It is about the psychological as well as the physiological, about illusion as well as reality. Darkness is not just the negative. It has its own presence and purpose. It can conceal and contain, create privacy and silence. And thus in darkness, like light, we find not just purpose, but a certain quiet beauty.

Mark Major is an architect and designer who works with light. He is a director of the award-winning, British design practice Speirs + Major.