But if his intellectualrigour forbids him making common cause with people he thinks are wrong, that perhaps only shows he is indeed the rottweiler of legend.
Both Mr Lafontaine and Mr Hombach published books on economics last year and they read, respectively, like rival tracts by Keynes and Milton Friedman (albeit with a mite less intellectualrigour in both cases).
Founded by a soldier turned mystic, Saint Ignatius Loyola, in the 16th Century, they have a tradition of intellectual and spiritual rigour which suggests that the Vatican is about to undergo a reset with huge implications for the future of the Roman Catholic Church in the 21st Century.