839. Apostasy is committed not only by those who leave the Church and join some contrary religion (e.g., Mormonism), but also by those who, while professing to be Catholics, assent to the non-Catholic principles of some society that claims to be philosophical, charitable, economic, patriotic, etc. Much more are those apostates who join societies that openly conspire against the Church. Such are: (a) Societies that are really non-Catholic sects, because they have an infidel or heretical creed--e.g., Freemasonry (which, according to its own authorities, is a brotherhood based on Egyptian mysteries and claiming superiority to Christianity), Theosophy (which is a conglomeration of nonsensical ideas about the Deity, Christ and Redemption), the Red International, whose aims are the destruction of property rights, etc; (b) Societies that are anti-Catholic sects, because their creed is hatred of the Church--e.g., the Orangemen’s Society, the Grand Orient, the Ku Klux Klan, Junior Order, etc. 840. The Sin of Doubt.--Faith as explained above must be firm assent, excluding doubt (see 752, 799), and hence the saying: “He who doubts is an unbeliever.” The word “doubt,” however, has many meanings, and in some of those meanings it is not opposed to firm assent, or has not the voluntariness or acceptance of error that the unbelief of heresy or infidelity includes. To begin with, doubt is either methodical or real. (a) Methodical doubt in matters of faith is an inquiry into the motives of credibility of religion and the reasons that support dogma, made by one who has not the slightest fear that reason or science can ever contradict faith, but who consults them for the purpose of clarifying his knowledge and of strengthening his own faith or that of others. This kind of doubt is employed by St. Thomas Aquinas, who questions about each dogma in turn (e.g., “Whether God is good”), and examines the objections of unbelievers against it; but unlike his namesake, the doubting Apostle, he does not withhold assent until reason has answered the objectors, but answers his own questions by an act of faith: “In spite of all difficulties, God is good, for His Word says: ‘The Lord is good to them that hope in Him, to the soul that seeketh Him’ (Lament, iii. 25).” (b) Real doubt, on the contrary, entertains fears that the teachings of revelation or of the Church may be untrue, or that the opposite teachings may be true.