 Once an efficacious combination is formed it may unite with other objects to form compounds productive of newly existing qualities. The causes of most familiar phenomena are formed from a large number of pre-existing objects and other circumstances (e.g., time) all of which are required to produce the observed effect. But the objects from which a cause is formed need not have qualities similar to those of the newly constituted cause. None of the qualities going into the compound may be retained and it may join with others to form many different masses of qualities. Still compound natures such as plants, animals, and the sentient principle (or mind) are not destroyed by entering into a succession of mixtures. 