Catholic Encyclopedia (1913)/Anima Christi
This well-known prayer dates its origin from the first half of the fourteenth century and was enriched with indulgences by Pope John XXII in the year 1330. All the manuscripts practically agree as to these two facts so there can be no doubt of their exactness. In regard to its authorship all we can say is that it was, perhaps, written by John XXII. Of this we are not certain, as this Pope has been falsely accredited with similar pious compositions, and a mistake could easily be made of confounding the one who gave the indulgence with the real author. The Anima Christi was and is still generally believed to have been composed by St. Ignatius Loyola, as he puts it at the beginning of his "Spiritual Exercises" and often refers to it. This is a mistake, as has been pointed out by many writers, since the prayer has been found in a number of prayer books printed during the youth of the saint and is in manuscripts which were written a hundred years before his birth (1491). James Mearns, the English hymnologist, found it in a manuscript of the British Museum which dates back to about 1370. In the library of Avignon there is preserved a prayer book of Cardinal Peter De Luxembourg, who died in 1387, which contains the Anima Christi in practically the same form as we have it to-day. It has also been found inscribed on one of the gates of the Alcazar of Seville, which brings us back to the times of Don Pedro the Cruel (1350-69) This prayer was so well known and so popular at the time of St. Ignatius, that he only mentions it in the first edition of his "Spiritual Exercises", evidently supposing that the exercitant or reader already knew it. In the later editions, it was printed in full. It was by assuming that everything in the book was written by St. Ignatius that it came to be looked upon as his composition. All this has been told at length by Guido Dreves (Stimmen aus Maria-Laach LIV, 493) and B. Baesten (Précis Historiques, XXXII, 630).