 Nash argued that his solution was the rational solution to bargaining problems because it is the only solution that satisfies four axioms that, he argued, any agents not involved in a bargain would select as desiderata for a bargaining problem: Pareto optimality, utility invariance, symmetry, and independence. An alternative justification is provided by Brian Barry who argued that if the bargaininers were to hire an independent arbitrator to determine how gains should be distributed, “each side will refuse to accept any arbitrator whose decision it expects to be less favourable than the outcome of direct bargaining ...[A]n arbitrator who is acceptable to both sides must be one whose decisions approximate the Nash solution” (Barry 1991: 26—27).