1. Meaning. Order is a unity of many elements systematically referred to each other. These must be different from one another but they must be in a possible relation to each other and in a real order also existent (Thomas Aquinas, De Potentia, q. 7, a. 11, c.). The unity need not be rounded off, but may be open — as in the series of natural numbers. The rule which determines how the elements follow or proceed from each other in a dynamic order is called for prefer…