When do labor unions and management bring in a mediator?

Les explains that when two parties have a controversy and cannot get together on a contract, as with labor unions and management, they bring in a mediator. The mediator's purpose is to make a meeting of the mind, to give here and give there, and finally agree and sign a contract. He contrasts this with God's covenant, saying God is not going to use a three-person mediation; God is the mediator, the instigator, and the fulfiller, and He alone is involved.