Letter 1561: The spiritual life is a journey with a beginning, a middle, and an end.

The usurper must be put down; and not so that those hearing this become idle, so to speak, but rather so that they apply themselves to the philosophical life — this has been said for that reason. For it is not because those who live rightly must be entirely free from reproaches that pleasure ought to be embraced, but because the best are altogether accused by the wicked, one must practice philosophy. For it is said not so that virtue may be fled from, but so that those who practice it may philosophize the more. For the one who attacks does not cause people to flee, but rather to contend more eagerly. Therefore, even if we are entirely subject to reproach, it is just to bear it patiently, for such rebuke suits the unrighteous fittingly. To Peter. Heresies arise from ambition and from obstinacy. From the love of ruling, I believe, and from preconceived opinion — two passions exceedingly hard to overcome — heresies have been born. For some, not deigning to be among the ruled, and others, after having been prejudiced, not consenting to be taught, have sown the seeds of novel doctrines, not deigning to abide by the established teachings.