" Where, then, is the discretion or the reason in loading burdens on the backs of those whose strength has not first been tested to make sure that the tasks assigned to human beings are in line with their natural constitutions? Would anyone give a donkey the same load as an elephant? Or the young or very old the same loads as full adults? Can the frail bear as much as the hardy, or the sickly as much as the well? "

― Pierre Abélard , Abelard and Heloise: The Letters and Other Writings