主要回勅集（アエテルニ・パトリス、プロウィデンティッシムス・デウス等を含む）

The popular demand for the Encyclicals and Apostolical Letters of a Roman Pontiff is something so novel as to constitute of itself a proof of the esteem in which he is held. It would seem that whatever is written of Leo XIII. in books or newspapers, instead of satisfying the universal desire for a knowledge of him, only inspires the wish to know more, and the conviction that the writings of a man of such powers and world-wide sympathies must contain messages of interest and benefit to all humanity. It is precisely the merit of the Letters of the late Pope that no matter when they were written, or to whom they were addressed, they are of actual and universal interest, as intelligible to the layman and illiterate as to the theologian and scholar, as urgent in their appeals to those who are not within the fold of which he was chief pastor as to the children of the household. His arguments could not but command attention, drawn as they were from history, experience, and reason, as well as from Scripture and tradition; and his sincere interest in the civil and social improvements of every nation, whether Catholic or not, made all hearken to his plea for religion as the chief factor of true progress.