Peace is not just a "subject, a theme", it's an immense opportunity for people, and it's a set of elements to be built upon. Its opposites - war, but also multiple forms of violence - are above all tragedies and threats, synonymous with suffering for many people and peoples on Earth. At the age of 25, and therefore rather late in life, I became aware of the fact that young people my age had known nothing but war in their lives or their survival. This, among other things, led me to try to contribute to thinking and acting for peace. At the same time, I gradually came to realize the close theoretical and practical links between peace and democracy, justice and the environment. In short, it was with a very strong sense of purpose that I tried to write this synthesis on the subject of peace.