 That is one version of the combination problem, but there are others. Consider one raised for a version of constitutive Russellian panspsychism, according to which microphenomenal quiddities, perhaps together with structural properties, combine to constitute macrophenomenal properties. The constitutive Russellian panpsychist is committed to the following two claims. First, corresponding to each instance of a microphenomenal quiddity underlying a physical disposition there is a unique conscious subject: a microsubject distinct from the microsubjects that correspond to other such instances of microphenomenal quiddities. Second, multiple microsubjects corresponding to microphenomenal quiddities combine to constitute a single macrosubject. But it is unclear how that second claim could be true. As William James (1890: 162) suggests, given any group of subjects and any further subject, it seems possible for the group to exist without that further subject existing. This is known the subject-summing problem (Goff 2009, 2017; Chalmers 2013, 2017; Coleman 2014).