 McLaughlin’s proposal is different, in a crucial respect, from Reid’s. It does not explicitly state that the property, which is the occupant of the functional role, is a property “unknown” to the observer. His proposal is designed to be “topic-neutral”. This means that colors could either be some complex physical properties, that could only be discovered by scientific investigation, or they could be the sort of properties described by Primitivists: sui generis, simple, intrinsic, qualitative, non-relational, non-reducible properties of physical bodies. McLaughlin argues that scientific investigation makes it highly plausible that the occupant of the role is some complex physical property—that is, that Color Physicalism is true—and that no good reason favors the Primitivist option.