What are the three most important purposes of a government established by a group of six people on a desert island?

create a direct democracy or a monarchy

Explanation:

being such a small group of people, a direct democracy could be created in which each person in the group votes whether or not they agree with the things they want to do, and if they want to have a leading leader, they could create a monarchy in the which leader says what to do and send other people to do the activities.

The foundation of our American Government, its purpose, form and structure are found in the Constitution of the United States. The Constitution, written in 1787, is the "supreme law of the land" because no law may be passed that contradicts its principles. No person or government is exempt from following it.