What is conversion? It's the change of a man's treasure, of a man's chief good. Till thou change thy chief good, it's in vain to complain of the disorders of thy heart; therefore, every unregenerate man may hence see the absolute necessity of conversion.
As the conversion of many people has taken place almost without observation, which often happens in the quieter walks of Christian life, and the conversion of a few only, who at first wandered far off, is incisive like that of an Augustine, such also is the case here. For the most part this witness works gradually and unobserved, and only in exceptional cases is it as lightning that suddenly flames through the skies.Sacred Theology, 560