I distinguish between active conversion by free choice and pragmatic conversion. Furthermore, I would like to distinguish between sudden conversions (“Pauline conversions”) and conversions that occur at the end of a more or less long process of alienation from one’s former religious affiliation (“Augustin conversions”). In historical reality, hybrid forms of these two extremes seem to be the rule. Con­version is a “faith change” that includes both so-called propositional attitudes (e.g. beliefs, religious beliefs, hopes, fears) and social preferences; I take Niels Stensen’s (1638-1686) conversion as an example.
Keywords: conversion, belief change, rational choice, Thomas Kuhn, Niels Sten­sen.