10 But to simulate and wish to lie hid; to bind men like slaves in the very tightest bonds, and without giving any sufficient reason; to make use of men enslaved to the will of another for any arbitrary act ; to arm men's right hands for bloodshed after securing impunity for the crime - all this is an enormity from which nature recoils. Wherefore, reason and truth itself make it plain that the society of which we are speaking is in antagonism with justice and natural uprightness. And this becomes still plainer, inasmuch as other arguments, also, and those very manifest, prove that it is essentially opposed to natural virtue. For, no matter how great may be men's cleverness in concealing and their experience in lying, it is impossible to prevent the effects of any cause from showing, in some way, the intrinsic nature of the cause whence they come. "A good tree cannot produce bad fruit, nor a bad tree produce good fruit."(12) Now, the masonic sect produces fruits that are pernicious and of the bitterest savour. For, from what We have above most clearly shown, that which is their ultimate purpose forces itself into view - namely, the utter overthrow of that whole religious and political order of the world which the Christian teaching has produced, and the substitution of a new state of things in accordance with their ideas, of which the foundations and laws shall be drawn from mere naturalism.
Source: Humanum Genus (Vatican.va)