 The first formulation of the quantity theory of money is often attributed to the jurist Martín de Azpilcueta, perhaps the best known Salamancan writer on economic issues. In an appendix to his manual for confessors, now published as On Exchange (1549 [2014]), he discussed exchange, supply and demand, and money. Azpilcueta attempted to explain the rampant inflation of the sixteenth century as connected to the large-scale input of specie from the New World. Goods, he argued, were more costly when money was abundant. This quantity theory of money was widely accepted throughout Europe.