36. An act is voluntary in its cause in two ways: (a) approvingly (physically and morally voluntary in cause), when one is able and obliged not to perform the act that is its cause (e.g., the quarrels of Caius mentioned above are approved implicitly by him, since he could and should prevent the intoxication which is their cause); (b) permissively (physically voluntary in cause), when one is not able or not obliged to omit the act that is its cause (see 94 sqq.). Examples: Balbus, in order to make a living, has to associate with persons of quarrelsome character, and as a result often hears shocking disputes. Titus, a military commander, orders an enemy fortification to be bombarded, although he knows that this will involve the destruction of other property and the unavoidable killing of some non-combatants or neutrals. Caius writes a book whose purpose and natural result is edification, but he foresees that evil-minded persons will misunderstand it and take scandal. 37. Omissions, as well as acts, may be voluntary. (a) Thus, they are directly voluntary, when they are willed as an end or as a means to an end. Example: Titus fails to reprove the disorders of those in his charge because he likes disorder, or because it illustrates his theory that everyone should go through an evolution from roughness to refinement. (b) They are indirectly voluntary, when their cause is willed with approval or permitted with disapproval. Example: Balbus does not like to miss Mass, but he fails to rise from bed when he hears the church bell ringing, and as a result does not get to church. If his failure to get up was due to laziness, the omission of Mass was approved by Balbus; if it was due to illness, the omission was only permitted. 38. The effect that follows upon an omission may also be voluntary. (a) Thus, it is directly voluntary, if the omission is chosen as a means to the effect. Example: Caius hears Titus say that he is going to make a certain business deal, and he knows that Titus will suffer a great loss thereby; but he wishes Titus to lose his money, and therefore says nothing about the danger. (b) It is indirectly voluntary, if one foresees the effect, and approves or permits it. Examples: Balbus sees Titus attacked by a hoodlum and realizes that, unless assisted, Titus will be badly beaten up; but he is such an admirer of pugilism that, in spite of his sorrow for Titus, he decides not to stop the fight. Caius sees his friend Sempronius drowning, and fails to go to his assistance, because to his regret he is not an expert swimmer. 39. The effect of an omission is indirectly voluntary and approved by the will when one is able and bound to do what one omits. Example: Balbus receives some confidential documents with the understanding that he will guard them sacredly; but fearing to lose the good graces of Titus, who is curious and loquacious, he omits to put the papers away as promised, with the result that Titus finds them and reads them.