Free Masonry

Membership in, and the activities of and international fraternity, ostensibly for mutual help and brotherly association, called the Free and Accepted Masons, having an elaborate ritual and system of secret signs. The fact that the Freemasons is a secret society is alone sufficient to make membership illegal for Catholics. Over and above this, it has received numerous papal condemnations, beginning with the constitution of Clement XII, In eminenti, in 1738, wherein it was declared that certain associations calling themselves Freemasons and other names made profession only of a natural religion, independently of any creed; that their objects and proceedings were completely secret, which was secrecy enforced by oath; that in the opinion of competent judges many members of such societies were discredited as unprincipled; and that several civil governments had already suppressed them as a public danger. (Definition from A Catholic Dictionary, 1951)
 

Church Teaching on Freemasonry:

• "The first warning of the danger was given by Clement XII in the year 1738,[3] and his constitution was confirmed and renewed by Benedict XIV.[4] Pius VII followed the same path;[5] and Leo XII, by his apostolic constitution, Quo Graviora,[6] put together the acts and decrees of former Pontiffs on this subject, and ratified and confirmed them forever. In the same sense spoke Pius VIII,[7] Gregory XVI,[8] and, many times over, Pius IX" Encyclical On Freemasonry by Pope Leo XII, 1884
• "At this period, however, the partisans of evil seems to be combining together, and to be struggling with united vehemence, led on or assisted by that strongly organized and widespread association called the Freemasons. No longer making any secret of their purposes, they are now boldly rising up against God Himself. They are planning the destruction of holy Church publicly and openly, and this with the set purpose of utterly despoiling the nations of Christendom, if it were possible, of the blessings obtained for us through Jesus Christ our Savior" Encyclical On Freemasonry by Pope Leo XII, 1884
• "If other proofs were wanting, this fact would be sufficiently disclosed by the testimony of men well informed, of whom some at other times, and others again recently, have declared it to be true of the Freemasons that they especially desire to assail the Church with irreconcilable hostility, and that they will never rest until they have destroyed whatever the supreme Pontiffs have established for the sake of religion." Encyclical On Freemasonry by Pope Leo XII, 1884
• "There is likewise a great danger threatening unity on the part of that association which goes by the name of Freemasons, whose fatal influence for a long time past oppresses Catholic nations in particular" Encyclical On the Reunion of Christendom by Pope Leo XIII, 1894
• "In view of these several reasons Catholics since 1738 are, under penalty of excommunication, incurred ipso facto, and reserved to the pope, strictly forbidden to enter or promote in any way Masonic societies. The law now in force [214] pronounces excommunication upon "those who enter Masonic or Carbonarian or other sects of the same kind, which, openly or secretly, plot against the Church or lawful authority and those who in any way favour these sects or do not denounce their leaders and principal members." 1917 Catholic Encyclopedia, Masonry (Freemasonry)
   

Summary

Prior Church teaching is clear; no Catholic may be a member or even condone membership in any Masonic society.