9 There are several organized bodies which, though differing in name, in ceremonial, in form and origin, are nevertheless so bound together by community of purpose and by the similarity of their main opinions, as to make in fact one thing with the sect of the Freemasons, which is a kind of center whence they all go forth, and whither they all return. Now, these no longer show a desire to remain concealed; for they hold their meetings in the daylight and before the public eye, and publish their own newspaper organs; and yet, when thoroughly understood, they are found still to retain the nature and the habits of secret societies. There are many things like mysteries which it is the fixed rule to hide with extreme care, not only from strangers, but from very many members, also; such as their secret and final designs, the names of the chief leaders, and certain secret and inner meetings, as well as their decisions, and the ways and means of carrying them out. This is, no doubt, the object of the manifold difference among the members as to right, office, and privilege, of the received distinction of orders and grades, and of that severe discipline which is maintained. Candidates are generally commanded to promise - nay, with a special oath, to swear - that they will never, to any person, at any time or in any way, make known the members, the passes, or the subjects discussed. Thus, with a fraudulent external appearance, and with a style of simulation which is always the same, the Freemasons, like the Manichees of old, strive, as far as possible, to conceal themselves, and to admit no witnesses but their own members. As a convenient manner of concealment, they assume the character of literary men and scholars associated for purposes of learning. They speak of their zeal for a more cultured refinement, and of their love for the poor; and they declare their one wish to be the amelioration of the condition of the masses, and to share with the largest possible number all the benefits of civil life. Were these purposes aimed at in real truth, they are by no means the whole of their object. Moreover, to be enrolled, it is necessary that the candidates promise and undertake to be thenceforward strictly obedient to their leaders and masters with the utmost submission and fidelity, and to be in readiness to do their bidding upon the slightest expression of their will; or, if disobedient, to submit to the direst penalties and death itself. As a fact, if any are judged to have betrayed the doings of the sect or to have resisted commands given, punishment is inflicted on them not infrequently, and with so much audacity and dexterity that the assassin very often escapes the detection and penalty of his crime.
Source: Humanum Genus (Vatican.va)