In 1931, under the title "Onward Industry," Messrs. James D. Mooney and Alan C. Reiley published a full-length book examining the comparative princip… - Lyndall Fownes Urwick

No superior can supervise directly the work of more than five or, at the most, six subordinates whose work interlocks. The reason for this is simple. What is supervised is not only the individuals, but the permutations and combinations of the relationships between them. And while the former increase in arithmetical progression with the addition of each fresh subordinate, the latter increase by geometrical progression. If a superior adds a sixth to five immediate subordinates he Increases his opportunity of delegation by 20 per cent, but he adds over 100 per cent to the number of relationships he has to take into account. Because ultimately it is based on the limitations imposed by the human span of attention, this principle is called The Span of Control.

To hold a group or individual accountable for activities of any kind without assigning to him or them the necessary authority to discharge that responsibility is manifestly both unsatisfactory and inequitable. It is of great Importance to smooth working that at all levels authority and responsibility should be coterminous and coequal.

At the present time administration is more an art than a science; in fact there are those who assert dogmatically that it can never be anything else. They draw no hope from the fact that metallurgy, for example, was completely an art several centuries before it became primarily a science and commenced its great forward strides after generations of intermittent advance and decline.