  It is, nevertheless, important to note that Aristotle restricts the principle of causational synonymy in different and subtle ways. Most significantly, an important domain of cases where a property of an object is actualised is exempted from the requirements of this principle. The actualisation of a property can be the continuation of a previous causal process to the extent that Aristotle claims it is a second actuality, following upon a previously acquired first actuality. In these cases the emergence of the second actuality does not necessarily require an additional external efficient cause. The operation of this first actuality, through which it reinforces and completes itself, can be the mere extension of the operation of the original efficient cause (this will be  Aristotle’s claim about the natural  locomotion of the elements, see  Section 5  below), or the entity which has acquired this first actuality can be already causally responsible for its own activities, including the ones which bring it to a level of higher  actuality[26]  (Aristotle’s examples for this case are  the soul of the embryo or of the newborn cub, which commands and  effects the nourishing and the activities of the animal; or the  actual application of a piece of knowledge one has acquired  beforehand). It is important to note that these claims are far from  trivial: they rest on further claims that the very definitions of  these first actualities (what it is to be an element, an animal, or  knowledge, respectively) inseparably include references to these  activities. 