This theory supposes that there must be, and supposedly always has been, a lower class for the upper classes to rest upon: the metaphor of a mudsill theory being that the lowest threshold (mudsill) supports the foundation for a building. This theory was used by its composer, Senator and Governor James Henry Hammond, a wealthy Southern plantation owner, to justify what he saw as the willingness of the non-whites to perform menial work which enabled the higher classes to move civilization forward. With this in mind, any efforts for class or racial equality that ran counter to the theory would inevitably run counter to civilization itself.