What are the dual purpose of owing Federalisation?

The federal system thus has dual objectives: to safeguard and promote unity of the country, while at the same time accommodate regional diversity. Therefore, two aspects are crucial for the institutions and practice of federalism. Governments at different levels should agree to some rules of power-sharing. They should also trust that each would abide by its part of the agreement. An ideal federal system has both aspects : mutual trust and agreement to live together.