There is nothing in which Men more deceive themselves than in what the World calls Zeal. There are so many Passions which hide themselves under it, and so many Mischiefs arising from it, that some have gone so far as to say it would have been for the Benefit of Mankind if it had never been reckoned in the Catalogue of Virtues. It is certain, where it is once Laudable and Prudential, it is an hundred times Criminal and Erroneous; nor can it be otherwise, if we consider that it operates with equal Violence in all Religions, however opposite they may be to one another, and in all the Subdivisions of each Religion in particular.

Joseph Addison (1672-1719) English essayist, poet, statesman

The Spectator, #185 (2 Oct 1711)
    (Source)