The prohibition against cruel and unusual punishment was not intended to carve into stone for the nation the sensibilities or practices of the 1780's. If it is not meant as a clear standard, what is its purpose?
It is a warning directed to those in power against being thought to be cruel or vindictive, and a reminder that when the government is thought to be cruel, it weakens its legitimacy. Monarchs have been thought to be stern and heartless in the past, but this is not the kind of social stability that is consistent with a free and equal society.
End Solitary Confinement.