Why a Catholic, in good standing, cannot also be a mason is a question that is often raised. From Dr Dianne Irving, professor of philosophy, theology and a trained bench scientist who performed research for many years:
["Note: I know, “lots of good people out there in these organizations doing good things.” But by far the majority are ignorant about and do not understand the higher dogmas (usually “secret”) and what they promote and teach. Yet their work is supporting them. Masonry is just one of such organizations. In common, most of these organizations have existed for many years, even centuries (especially in the East and Middle East), and are ultimately grounded on ancient and post-Christian gnosticism -- all of which are, among other things, very anti-Christian.
"They are all pagan polytheistic pantheistic MYTHS, with totally different “cosmologies” than ours, going back at least 5000 BC (the myth of Okeanus). Look it up for yourself; not new, not secret any more.
"In fact, if you know the universal symbols for gnosticism (used for communication among themselves for centuries), then you will quickly come to realize that gnosticism in multiple forms is drowning our cultures -- all over the TV, Hollywood, plays, music, books, especially our kids materials.
"The current issues in genetic engineering, surrocacy, futurism, transhumanism, homosexuality, human embryo research, etc. are overtly grounded in gnosticism. See Hans Jonas, The Gnostic Gospels; St. Ireneus, Against the Gnostics (the Nicene Council was formed to address the mass of gnostic heresies in the early Church); Hans Jonas’ article in Encyclopedia of Philosophy in Irving, "GNOSTICISM, the Heretical Gnostic Writings, and 'Judas'" (April 9, 2006), at: http://www.lifeissues.net/writers/irv/irv_121gnosticism1.html.
"For an interesting look at Masons, see article/podcast http://archive.org/details/FreemasonryByRalphEpperson.
"Similarly, many Popes, including Pope Leo XIII, have understood with crystal clarity the enormous damage caused by the gnostics for multiple centuries.
"Given the recent complaints about Catholics (e.g., Knights of Columbus, Jesuits) being members of the Masons, the following still-authoritative encyclical of Pope Leo XIII is instructive.
"Note that he was repeating the warnings of previous Popes – Clement XII in 1738, Benedict XIV in 1751, Pius VII in 1821, Leo XII in 1826, Pius VIII in 1829, Gregory XVI in 1832 and Pius IX in 1846 and 1865 and on four other occasions. After Leo XIII St. Pius X in 1911 confirmed this condemnation.
"Altogether, Leo XIII spoke out five different times against Freemasonry, but especially in the encyclical Humanum genus (copied in full below). All these Popes say that a Catholic cannot be a Mason. Time to wake up and call a spade a spade -- the best kind of pastoralism." -- DNI]
Pope Leo XIII had a vision of hell during his papacy and from that experience composed the Prayer to St Michael, recited after all Masses from that time on (and at the end of the Rosary) until introduction of Pope Paul VI’s Novus Ordo Missae in 1969. The prayer continues to be read after the Tridentine Rite Mass where it is offered.