Augustinus dicit, in II Confess., "timor insolita et repentina exhorrescit, rebus quae amantur adversantia, dum praecavet securitati," quia obiectum timoris est malum imminens quod non de facili repelli potest. Hoc autem ex duobus contingit, scilicet ex magnitudine mali, et ex debilitate timentis. Ad utrumque autem horum operatur quod aliquid sit insolitum et repentinum.
Augustine says (Confess. ii, 6): "Fear is startled at things unwonted and sudden, which endanger things beloved, and takes forethought for their safety," because the object of fear is an imminent evil, which can be repelled, but with difficulty. Now this is due to one of two causes: to the greatness of the evil, or to the weakness of him that fears; while unwontedness and suddenness conduce to both of these causes.
Primo quidem, facit ad hoc quod malum imminens maius appareat. Omnia enim corporalia, et bona et mala, quanto magis considerantur, minora apparent. Et ideo, sicut propter diuturnitatem dolor praesentis mali mitigatur, ut patet per Tullium in III de Tusculanis quaest., ita etiam ex praemeditatione minuitur timor futuri mali.
First, it helps an imminent evil to seem greater. Because all material things, whether good or evil, the more we consider them, the smaller they seem. Consequently, just as sorrow for a present evil is mitigated in course of time, as Cicero states (De Quaest. Tusc. iii, 30); so, too, fear of a future evil is diminished by thinking about it beforehand.
Secundo, aliquid esse insolitum et repentinum facit ad debilitatem timentis, inquantum subtrahit remedia quae homo potest praeparare ad repellendum futurum malum, quae esse non possunt quando ex improviso malum occurrit.
Secondly, unwontedness and suddenness increase the weakness of him that fears, insofar as they deprive him of the remedies with which he might otherwise provide himself to forestall the coming evil, were it not for the evil taking him by surprise.
Illi qui habent iram acutam, non occultant eam, et ideo nocumenta ab eis illata non ita sunt repentina, quin praevideantur. Sed homines mites et astuti occultant iram, et ideo nocumentum quod ab eis imminet, non potest praevideri, sed ex improviso advenit. Et propter hoc philosophus dicit quod tales magis timentur.
Those who are quick-tempered do not hide their anger, wherefore the harm they do others is not so sudden, since it may be foreseen. On the other hand, those who are gentle or cunning hide their anger, wherefore the harm which may be impending from them, cannot be foreseen, but takes one by surprise. For this reason the Philosopher says that such men are feared more than others.