Ideally a just constitution would be a just procedure arranged to insure a just outcome.
The claims of existing social arrangements and of self interest have been duly allowed for. We cannot at the end count them a second time because we do not like the result.
Peace surely is a good reason, yes. But there are other reasons too.
A just system must generate its own support.
A society regulated by a public sense of justice is inherently stable.
An intolerant sect has no right to complain when it is denied an equal liberty... A person's right to complain is limited to principles he acknowledges himself.