In his response to Pat Gunning, Gary Mongiovi wrote: "The theory of demand & supply is a post-1850 development ..." Gary thus excludes Smith, Ricardo, Malthus, and Mill from developers of the supply and demand theory of exchange values or price. I read Smith's Book 1, chapter 7 as the culmination of his explanation of market price determination begun from chapter 5 of the same book. Ricardo also affirms that "the 7th chap. of [Smith's] Wealth of Nations" is where "all that concerns this question [of value or price determination] is most ably treated" (_Works_, 1: 91). Malthus (1936, 62) argues that "the value of commodities in money or their prices are determined by the demand for them, compared with the supply of them. And this law appears to be so general, that probably not a single instance of a change of price can be found, which may not be satisfactorily traced to some previous change in the state of the demand or supply." Mill (_Works_, 3: 467-68) also explains market price determination by supply and demand, applying a "mathematical analogy ... of an _equation_. ...If the demand increases, the value rises; if the demand diminishes, the value falls off falls: again, if the supply falls off, the value rises; and falls if supply is increased." Pat Gunning's response to Gary, including arguing that "demand and supply reflect a shift from a classical to a neoclassical approach the the subject matter ..." appears to acquiesce with Gary's claim. So, I'd like to ask, In what sense was the theory of demand and supply as an explanation of market price determination a post-1850 development? James Ahiakpor