  Within the four domains where genuine change can occur, change always requires the existence of a potentiality which can be actualised.  But change is neither identical to this potentiality, nor to the lack of a property, nor, without further qualifications, to the actuality which is acquired when the potentiality is actualised (Physics 3.2, 201b33–35).  It is a special kind of actuality, the actuality of the potential in so far as it is potential (Physics 3.2, 201a27–29). Aristotle’s formulation strongly  suggests that the potentiality actualised in the process of change is  not a separate and independent potentiality for motion, alongside the  entity’s potentiality for harbouring the  end-state of the process: the process, say, house-building, and the  end result, the house, are different actualisations of the same  potentiality of a set of materials that is buildable into a house.   Not only would Aristotle’s definition be uninformative otherwise, amounting to the tautologous claim that change is the actualisation of the capacity for change, the further qualification in the definition, that change is the actuality of the potential in so far as it is potential, would be completely idle.[16] This further restriction is easiest taken as selecting between the different types of the realisations of the same  potentialities.[17]   As Aristotle stresses these are the incomplete actualities belonging to these potentialities, because what is actualised in a process of realisation is an incomplete potentiality only (Physics 3.2, 201b32–33).  Accordingly, potentialities of change are admitted into the ontology. They, nevertheless, do not need to feature as potentialities in their own right, but as the incomplete variants of the fundamental potentiality for an end   result.[18]