Think of the Thirdside as five "P"s.
PEOPLE from the community. Unlike the ultimate arbiter in the form of a king or authoritarian state, the third side is not a transcendent individual or institution who dominates all, but rather the emergent will of the community. It is an impulse that arises from the vital relationships linking each member and every other member of the community.
Using the POWER OF PEERS. The third side possesses the power of peer pressure and the force of public opinion. It is people power. It uses the power of persuasion. It influences the parties primarily through an appeal to their interests and to community norms.
In every conflict, there usually exists not just one possible third party but a multitude. Individually, we may not be able to intervene effectively, but collectively we are potentially more powerful than any two conflicting parties. Organizing ourselves into a coalition, we can balance the power between the parties and protect the weaker one.
From a PERSPECTIVE of common ground. While most issues in contention are presented as having just two sides - pro and con, there usually exists a third. From this third perspective, the truth of each competing point of view can be appreciated. Shared interests often come to loom larger than the differences. People remember that they all, in the end, belong to the same extended community.
Supporting a PROCESS of dialogue and nonviolence. Silently or loudly, the Third Side says "No" to violence and "Yes" to dialogue. Thirdsiders urge disputants to sit down and talk out their differences respectfully. They focus, in other words, on the process. To them, how people handle their differences is just as important as what outcome they reach.
Aiming for a PRODUCT of a "Triple Win." Thirdsiders strive for a resolution that satisfies the legitimate needs of the parties and at the same time meets the needs of the wider community. The goal of the third side is, in other words, a "triple win."