Answer to Question 1
Federalism assumes that by giving minority groups some voice at the local level, they will be more willing to negotiate on other issues at the national level. A federal constitution can, if designed well, promote political stability in a country that has multiple competing ethnic, religious, or other political identity groupsa country that might otherwise collapse into civil war or split into several smaller, weaker countries. For example, Canada's federal constitution provides the French-speaking province of Quebec with some measure of autonomy from the central government, which is dominated by politicians from the English- speaking provinces. Federalism also works to limit political tension in India, an ethnically, linguistically, and religiously diverse country. Under a unitary constitution, minority groups in India, Canada, or elsewhere might fear loss of their group's autonomy to set education policies or worship as they please, for example.
Answer to Question 2
To find a balance between limited and effective government, Madison famously advocated establishing political institutions that check and balance politicians' ambitions against each other, so that no one person or group could concentrate enough power to overwhelm individual freedoms. This idea is fundamental to the U.S. Constitution, and as a result, political institutions in the United States tend to fragment, decentralize, and consequently weaken the central government's power.