Is the "Just Price" an Antiquated Notion?
Livio Di Matteo has a nice discussion of the history of supply-and-demand analysis here . Along the way, the idea of a "just price" arises, and is regarded, both by Di Matteo and commenter Bob Murphy (probably no relation to the Murphy we know and love) as an antiquated idea, incompatible with modern price theory. But perhaps just price theories are not incompatible with supply-and-demand analysis. My reading of Aristotle (from whom Aquinas would have drawn his basic notions) suggests to me that what he was looking at (without having the terms, of course!) was producer and consumer surplus, and the "equality" that had to hold was between these surpluses, so that if I would buy at any price under $2, and Murphy would sell at any price above $1, the just price should be around $1.50. "Unjust" prices would come about when one of us has far greater bargaining power, and "forces" the price to $1.01 or $1.99. To consider this in more concrete term...