Ben Carson's perturbing notion of 'involuntary immigrants', in chains yet somehow still dreaming of a new life, flags up what was possibly the key debate on human liberty in the seventeenth century.
In the Republican model of libertas, largely inherited from the Romans, the mere presence of arbitrary power implies a loss of individual freedom.
Others such as Thomas Hobbes however, were to effectively question whether a slave whose own choices never happened to be in conflict with the will of his or her master, was really a slave.
Of course this was all part of a wider debate about executive authority, which is not without contemporary relevance.
The English Parliament or legislature had rebelled against the sovereign because in both words and deed he had indicated that he was laying claim to a form of discretionary and thus arbitrary power.