materially in the sin of another. This doctrine may be applied to the matter before us, and so though it is never lawful to help another to do what is always and intrinsically wrong, as to kill an innocent person, yet in other cases it is not sinful to co-operate materially with the unjust action of another. A servant who is threatened with instant death unless she gives up a key to a robber, or shows where her master's money is kept, would act heroically if she died rather than betray her trust; she would not commit sin if she preferred her own life to her master's property.
6. On account of one's office, or in virtue of a special contract, there is sometimes a special obligation to prevent injury being done to others, and if the obligation be not fulfilled, there is negative co-operation in the injury inflicted. Apart from such special office or contract we are bound in charity to prevent injury to others as far as we can, but not in justice. This negative co-operation may be committed by concealment of injustice which has been done, as when a servant conceals thefts committed against his master's property which has been entrusted to his care. It may be committed by silence, as when a policeman accepts hush money to say nothing about a robbery. It may also be committed if one whose duty it is to protect another's rights or property neglects that duty and allows them to be injured. On account of defence of an unjust act which has already been done there will not arise an obligation to make restitution, unless such defence was the cause why restitution was not made for the crime defended. All approbation and defence of wrongdoing is nevertheless sinful. One who culpably neglects to prevent his animals from doing harm to his neighbour is bound to make restitution.
Sometimes these negative co-operators are excused from performing their strict duty on account of the very serious inconvenience to which it would subject them, and which they are not presumed to have obliged themselves to undergo. In such cases they will be excused from making restitution for injuries which they did not prevent.
