The cause of this outbreak of fraternal solidarity in a community which has not always be dominated by mutual admiration, is the seriousness of the crisis we face.
At the Synod in the Autumn, we have every reason to believe that a small number of Cardinals will be pushing their agenda, to admit the divorced and 'remarried' to Holy Communion.
That matters. In the first place, it matters because of what it says about marriage: that a valid, consummated marriage is not life-long and dissoluble only by death. At a time when marriage is being redefined out of existence in secular society, it is scarcely credible that any Cardinal of the Church should think this a good idea. But some do.
In the second place, it matters because it attacks the Eucharist. The implicit message is that the Eucharist is about communion with the community: we must not (horror of horrors) exclude anyone. But we know the reality is that the Eucharist is about communion with Christ (and thereby with each other): that unless we are committed to striving to conform ourselves to Christ (that is repenting of our sins and struggling against them) then we receive Holy Communion at our great peril.
But there is more. This movement also attacks the very foundations of the Church. We believe the Church to be One, Holy, Catholic, and Apostolic. This movement undermines each of those four marks of the Church.
The unity of the Church is visibly attacked by those German bishops who proclaim that they will go down this path regardless of what the Synod fathers say. Such a unilateral declaration of independence is a grave sin against the unity of the Church. So, too, is any distinction created between the Church's teaching and her practice: that would wound the integrity of the Church.
The Holiness of the Church is attacked by this proposal because her holiness derives from her identity as the mystical body of Christ. Yet if she were to separate herself from Christ, who clearly stated that whoever divorces and remarries commits adultery, then she would separate herself from holiness.
The Catholicity of the Church is, in part, seen in her being the teacher of truth for all peoples, in all places, at all times. Were she to allow tomorrow what she has always proclaimed gravely sinful, that claim to Catholicity would be corrupted.
The Apostolic nature of the Church is precisely her function of handing on to each new generation the Faith received from the Apostles. That includes such unfashionable sentiments as 'For he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord.' To contradict that is to deny the Apostolic nature of the Church.
And then there are the effects of such a move. Who can doubt that, however much it be motivated by compassion in hard cases, it would lead, as every liberalising move ever made has always led, to an abandonment of the principle at stake.
The price will be paid by women abandoned by their husband, and men abandoned by their wife; and above all by children, deprived of proper parenting, and of any understanding that human love can, with the grace of God, endure and grow, if fidelity is made primary, above sentimental notions of love.
So the stakes are high: if you have not yet signed the letter, please do so now.