What did Oakes mean by his statement: “Alcatraz is not an island it’s an idea”?

On November 9, 1969, Richard Oakes, Akwesasne Mohawk, and a group of Native American supporters set out in the Monte Cristo, to symbolically claim the island (Alcatraz) for the Native American people. Oakes' declaration that “Alcatraz Is Not an Island" defined the occupation.... as it wasn't so much about the "occupation", as it was about justice and a better life.... a life of self -government and self-determination.