Minorsky’s PID algorithm and the control of complex systems

A classic quote from Dante’s Divine Comedy is ‘Ahi serva Italia, di dolore ostello, nave senza nocchiero in gran tempesta’ (Ah enslaved Italy, vale of tears, ship in great storm with no helmsman). Over the past few years many of us have felt a rising anxiety about what the future holds, as strange currents have pushed our countries into ‘uncharted waters’. How stable is our world?