Ernest Gowers, The Complete Plain Words
(1954; rpt. Baltimore: Penguin Books, n.d.), p. 128, s.v. ideology
This word offends some purists, but I do not see why it should, provided that its mesmeric influence is kept in check; the old-fashioned creed or faith may sometimes serve. But now that people no longer care enough about religion to fight, massacre, and enslave one another to secure the form of its observance, we need a word for what has taken its place as an excitant of those forms of human activity, and I know of none better.
If Gowers were alive today, he might change his mind about religion, what people think about it, and what they do in its name.