Pareto optimality: No one can become better off, without someone else becoming worse off. People will keep exchanging until they optimize the collection of things they possess that is, they will keep trading until they can’t improve their situation further. Then they will stop, because no one wants to make a trade that makes them worse off. Everyone maxes out able to trade away, and we get better off until we have nothing left to trade. Will reach an equilibrium.
Everyone will be better off via exchange. (justification) Everyone will improve with utility.
