Cœuré and Pisani-Ferry’s paper could be retitled, “In search of common international economic policy principles.” Their plea is not for an explicit commitment to coordination, which is, according to them, “too demanding.” They are looking for a softer approach to coordination. I question whether constant exchange rates can be established in this way. I begin by asking what would have to be done if we want stable exchange rates. Next, I show that the necessary conditions will not be achieved. Thus, my argument is a contrario.