The publication of this collection of Papal pronouncements and correspondence relating to the union of Christendom could not have been better timed. The explosion of ‘Father Jerome’s’ squib has alone been sufficient to blow away whatever cobwebs may have been thought to have gathered round Satis Cognitum and Apostolicae Curae. The new Anglican endeavour towards understanding with Christians on the Continent through the pages of (Ecumenica makes the reappearance of Leo XIll’s utterances about the A.P.U.C. and Pius XI's Mortalium Animos singularly opportune.

Quite apart from the authority which belongs to these documents, an authority which establishes them permanently as the basis of every Catholic endeavour to forward the union of Christendom, they possess an intrinsic quality which puts them in a place which is unique in the literature of reunion. It is nothing less than a burning passion for the cause of Christian unity which flames up in Pope Leo's Encyclical Praeclara Gratulationis and his moving letter to the English People Amantissima Voluntatis. Despite the formal language of pontifical docunicnts, which reads so stiffly in translation, it is difficult to find a parallel in the writings of Catholic or non-Catholic reunionists to the warmth of Pope Leo’s appeals.

The reason is not far to seek. For Leo XIII the unity of Christendom was a matter not merely of expediency, however urgent, though nobody realized better than he did, as pages of Praeclara Gratulationis show, how urgent was the need for unity in the face of modern conditions.