Louis Bouyer var i mange år også involvert i økumenisk arbeid (han hadde jo selv konvertert fra den lutherske kirke), der han hadde noen gode og noen dårlige erfaringer. Har skriver slik om dette i sitt kapittel om Vatikankonsilet:
More comforting, though still a mixed bag, would be my experiences in ecumenical matters before, during, and after the Council.
As soon as I had come into the Catholic Church, and even before that, it had been easy for me to notice that as far as the Catholic pioneers of ecumenism were concerned (except for Dom Lambert Beauduin, Dom Clement Lialine, or Father Christophe Dumont, OP), and also as far as its most tenacious enemies were concerned, such as, at the time, the future Cardinals Bea, Journet,’ or Paul Philippe, simply being a convert disqualified one from being involved in these issues. For the former, this stemmed from the idea of ecumenism, creeping at the time, triumphant today, that Eric Masca has quite accurately dubbed «Alice in Wonderland Ecumenism»: «Everybody has won, and all must have prizes!» In other words: it is out of the question that anything should change on either side, the important thing being to agree that one may behave or believe as he pleases, as long as all end up thinking that the whole business is unimportant, «yes» and «no» being equivalent answers to every question.
As for the latter group, their suspicion obviously consisted in the possible temptation for converts that all was not false in their original Protestantism after all, and that it might be well to bring something of it into the Catholic Church.
… When the Council resumed after the death of John XXIII, his successor would have liked to call me to it as expert at the Secretariat for Unity. But I had broken with the Institut catholique de Paris too recently to run the risk of renewing the good Fathers’ bitterness; furthermore, the turn that some interventions were taking, on the part of certain personalities from among those who were hogging the limelight at that Council, did not make me wish to follow any more closely debates whose confusion was daily increasing. …