To answer James Ahiakpor's question: In Smith & Ricardo, price is regulated by production costs, with the real wage treated as more or less parametric, i.e. not determined by the interaction of price-elastic factor demand curves with given resource endowments. There is no presumption that market forces clear the labor market, a vital element of neoclassical S&D theory. There is no notion that the behavior of buyers or sellers can be depicted as well-defined functions of price. (In Ricardo there are passages which explicitly cast doubt on this.) The mechanism described in Smith's chapter 7 explains how market forces bring the market price of a good into line with the natural price; but the latter is not DETERMINED by that mechanism. Perhaps more to the point, Ricardo states quite clearly, in CH. XXX of the Principles, that deviations between S&D explain deviations between market price and long-period normal price, and that the latter is not determined by the forces of S&D but by cost of production: he is here explicitly rejecting Malthus's theory, so James errs, I believe, in placing them together on this issue. If we take Ricardo at his word, as we should, he had a very different theory in mind from modern textbook S&D theory.
 
Malthus is a different matter. He sometimes writes as though he has a primitive S&D theory in mind, and for this he drew criticism from Ricardo and scorn from Marx, who lumped that kind sort of reasoning under the heading of "vulgar economy"--the sort of superficial analysis that says only what is obvious, that market prices respond to gaps between the quantity available of a product and the amount desired. 
 
I was careful to say that S&D theory, as a coherent account of how markets regulate value & distribution--as opposed to the superficial story about movements in market price that every shopkeeper and mercantilist writer with a pair of eyes in his head could grasp--was not embraced by most economists until after 1880 or so. We do find earlier traces. Malthus & Say hint at it. JS Mill points in that derection as well, and offers a more carefully worked-out rationale; the first edition of his Principles was published in 1848, a shade earlier than 1850, but "close enough for government work" as grandad used to say. 
 
My main point was that Smith, Ricardo, Marx, Petty, and let me add now, Cantillon and the Physiocrats, had a very different understanding from modern economists of how of relative prices and income distribution are determined. I was querying how, in light of this, they fit into Pat's definition of what falls within the proper scope of economics.
 
Gary Mongiovi