As Our Predecessors have many times repeated, let no man think that he may for any reason whatsoever join the Masonic sect, if he values his Catholic name and his eternal salvation as he ought to value them. Let no one be deceived by a pretense of honesty. It may seem to some that Freemasons demand nothing that is openly contrary to religion and morality; but, as the whole principle and object of the sect lies in what is vicious and criminal, to join with these men or in any way to help them cannot be lawful
Pope Leo XIII (1990). “A Light in the Heavens: Great Encyclical Letters of Pope Leo XIII”, p.76, TAN Books