He knew the horrors of World War II, of being a refugee, of the Nazi occupation in France, imprisonment and escape from prison.
In 1948, he entered and won an essay contest on how to govern the world, the prize of which was an internship at the newly created United Nations.
He devoted the next 40 years of his life behind the scenes at the United Nations, focusing his energies on nurturing a better world, including working for the environment, economics and peace.
In addition to his duties at the University for Peace, he devoted time to his writings and was an internationally acclaimed, multilingual speaker[10][11] and author of fourteen books published in various languages.
At the prompting of many of his friends, admirers and non-governmental organizations, Muller was a candidate as a global citizen in 1996 for the post of Secretary-General of the United Nations.