 A difficulty for this approach is that most philosophers don’t think there can be one-many identity relations. Some think identity is of necessity a one-one relation, although others allow there can be many-many identity; for instance, it may be that the three men who committed the robbery are identical to the three men who were convicted of the robbery. Those who believe identity can be one-many typically do so because they accept the controversial thesis that composition (the relation of parts to a whole they compose) should be understood as identity. Although Bøhn does accept that thesis (Bøhn 2014), he argues that this Trinity theory relies only on our having “a primitive notion of plural identity” (371), that is, a concept we understand without reference to any concept from mereological (parts and wholes) theory. For example, we can recognize a certain human body to be identical to a certain plurality of head, torso, two arms, and two legs. And we can recognize that a pair of shoes is identical to a plurality of shoes (365).