Demand-Demand Equilibrium

The basic unit of Economic activity is the Exchange, and not the mere transfer, e. g. a donation.  Now, while in a simple Exchange, each party has both a Supply and a Demand, the Psychological motors, according to Smith, of the negotiation that precedes it, are the Demands involved, e. g. the seeking by each party of Profit.  Hence, the Equilibrium reached by the negotiation is Demand-Demand. not Supply-Demand, as Smith and his followers commonly conceive it.  Likewise, the distinction usually represented as 'Supply-Side' vs. 'Demand-Side', is actually that between two different Demand-Sides.