 One objection often made against the theory is that bundles are mereological sums, rather like Locke’s ‘masses of matter’, and that, therefore, any change of property is a change in the identity of the object. Various forms of essentialist solutions to this problem have been suggested, for example, by Simons (1994), and Barker and Jago (2018). I must admit to having difficulties seeing why the view that objects are constituted solely out of property-instances should commit one to a mereological view, any more than the theory that they are constituted solely from material particles would, so I do not see this as a special problem for the bundle theory.