When Leo XIII promulgated Aeterni Patris in 1879, he stipulated that the "Leonine," or official, edition of the Summa should always be printed in conjunction with Cajetan's Commentary. For five hundred years they were studied together. Generations were trained by reading through the Summa article by article with Cajetan's commentaries in hand. Early printed editions of the Summa typically included them in a Talmudic arrangement, as marginal text running around each article by Aquinas. This edition imitates that example. Recently, serious thinkers of all denominations—and none—have found...

When Leo XIII promulgated Aeterni Patris in 1879, he stipulated that the "Leonine," or official, edition of the Summa should always be printed in conjunction with Cajetan's Commentary. For five hundred years they were studied together. Generations were trained by reading through the Summa article by article with Cajetan's commentaries in hand. Early printed editions of the Summa typically included them in a Talmudic arrangement, as marginal text running around each article by Aquinas. This edition imitates that example. Recently, serious thinkers of all denominations—and none—have found...