"The remarks on negative entropy have met with doubt and opposition from physicist colleagues. ...[I]f I had been catering for them alone I should have let the discussion turn on free energy instead. It is the more familiar notion... [b]ut seemed linguistically too near energy for... the average reader... the concept is a rather intricate one, whose relation to Boltzmann's order-disorder principle is less easy to trace... '[E]ntropy with a negative sign'... is not my invention. It... [is] precisely the thing on which Boltzmann's original argument turned."