In his answer to Robin Neill's "query", Tony Brewer rightly  
identifies "neutrality" with the "equiproportionality/no long-run  
real effects" propositions", and refers to Hume's awareness of two  
"exceptions" to neutrality (i.e. the open economy and the short-run). 
It may be interesting to notice that the "Austrians", von Mises and  
von Hayek, proposed a criticism of the "equiproportionality  
proposition" based upon the distinction between comparative statics  
and dynamics, thus going well beyond the two "exceptions" considered  
by Hume. 
 
In his criticism of Hume (and other authors supporting what he  
defined the "mechanical version" of the Quantity Theory) Mises wrote  
"There is no justification whatever for the widespread belief that  
variations in the quantity of money must lead to inversely  
proportionate variations in the objective exchange value of money, so  
that, for example, a doubling in the quantity of money must lead to a  
a halving in the purchasing power of money" (Mises (1971: 139-145;  
206-212). 
 
He was explicit that the equiproportionality proposition holds true  
only in a comparative static sense, but not in the dynamic sense:  
doubling the quantity of money in a country will not lead to a  
doubling of the price level, since the latter view implies the  
untenable assumption that the new money is distributed exactly in  
proportion to each individual's existing money holdings , which is  
equivalent to assuming distributional effects away. In reality, the  
new money is always injected into the system at particular points.  
Consequently, the relative wealth of individuals is affected, and so  
are relative prices: the relative prices of the goods favoured by  
individuals whose real wealth has increased rise more than those of  
the goods favoured by individuals whose relative wealth has fallen.   
(Mises, 1971, [1924],  p.207; pp.139-140). Thus, the effects of money  
on relative prices and its distributional effects are parts of the  
same process. 
 
Mises, The Theory of money and credit, The Foundation for Economic  
Education, Irvington-on Hudson, New York, 1971. 
 
Lilia Costabile