apostatize

v. i. [ imp. & p. p. Apostatized p. pr. & vb. n. Apostatizing. ] [ LL. apostatizare. ] To renounce totally a religious belief once professed; to forsake one's church, the faith or principles once held, or the party to which one has previously adhered. [ 1913 Webster ]

He apostatized from his old faith in facts, took to believing in &unr_;emblances. Carlyle. [ 1913 Webster ]