If your state of being is one of contentment--no matter what circumstance puts before you--you may even find contentment when life gives you nothing. Even in adversity. It's a mark of maturity. I believe the word nothing here is not being used mathematically, but instead to show the difference between a person who can find contentment without needing things outside of self.

It would be good to know the context in which the statement had been made or written, but I agree with the statement. There are people for whom acquisition has little importance, and there are those who have suffered dire circumstances, but who have had such an unusual degree of inner strength that they have found contentment--peace of spirit--that calls forth admiration and even encouragement from some of us not so equipped.

If the statement is taken too literally and to the extreme, it will fall into a pit of absurdity. But it can be taken pretty damned far and still there will be examples of people who have maintained a state of contentment. Some of the stories of the holocaust show incredible instances of individuals who maintained equanimity and peace because of deep faith. And other similar instances of people in prison camps where they were tortured, but still found inner contentment almost always--from what I've read--because of deep faith.

So, I would guess that Nicolas Boileau-Despreaux is writing of a matter of degree here of inner peace, contentment, maturity of character, and spirit.