In Josef Pieper’s brilliant little book On Hope, there is a puzzling remark on the Patristic term “chaste fear” (timor castus) for the filial fear of God. He says the term is “no longer wholly comprehensible to us today” (“eine…unserem Verständnis nicht mehr ganz erschließbare Wortverbindung”). This remark is puzzling because the distinction that Pieper goes on to make between servile fear and filial fear as based on the love of concupiscence and the love of benevolence seems to give a perfectly obvious reason for giving filial fear the name “chaste.” It is surely not too difficult to see why one would call the love of benevolence, the love that wishes well to the one loved, “chaste” when one is distinguishing it from the love of concupiscence that desires to enjoy the beloved. (Although of course, one has to emphasize that the love of concupiscence is not necessarily “unchaste” in the sense of the sin of unchastity; both sorts of love are necessary). And so it makes sense that one would carry the epithet “chaste” from the love to the fear that is founded in it.
Servile fear is the fear of the slave who fears to hear from the master: “I do not know you, depart from me.” It is the fear not only of the punishment of the senses in damnation, but above all of of the essential punishment of damnation: the absolute loneliness of being deprived of the vision of God. The slave once to behold the master whom he loves, and he wants to be known and approved of by the master. He wants the master to give him glory, doxa, recognition: “You good and faithful servant.” And he is afraid of the eternal loss of that glory— eternal shame and bitterness.
Filial fear is the fear of the son who fears that anything be done against the beloved Father. It is the fear above all that he should himself do anything against the Father. It flows from desire for the good of the beloved, not for desire for the son’s own good.
This shows why both forms of fear are necessary as long as we are in via, and have not arrived at our heavenly goal. “Chaste fear” should become ever more dominant, but servile fear ought not to pass away entirely, because we ought to desire our own union with God, and the unspeakable happiness of attaining to the one whom we love.