 The productive aspect of an object is called a “power”, defined as a productive principle, or “property which lies in the secret nature of objects” and determines the qualities which will be perceived if the object unites with various other objects and the natures that constitute a perceiver (ERCE: 64). Fantl (2016: 97) maintains that powers are basic in Shepherd’s metaphysics suggesting that objects are fundamentally constituted by activities, or forces of the sorts envisaged by Leibniz or Priestly. 