Section — Slater, Manual of Moral Theology
Section II. How Much is to be Restored
We have already seen what must be restored in the case of one who is in possession of another’s property, or in case of unjust damnification to another. In general, the damage inflicted is the measure of the restitution to be made, for justice requires that the owner should have back his own. When there were several who co-operated in injustice a special difficulty arises as to whether each and all are jointly or severally bound to make restitution. If two thieves assist each other to break into and rob a house, what are the obligations of each of them with respect to the restitution to be made ?
p. i, 274
In such cases as this each must, of course, make restitution for the harm which he personally and immediately caused. If each one takes his share and makes reparation for that portion of the injustice which he committed, the whole damage will be repaired. But sometimes some of the partners of injustice are unable or unwilling to make restitution for their share in the unjust act; the question then arises whether the rest are bound to make good the whole damage inflicted.
Each and all will jointly and severally be bound to make reparation for the whole damage, or in solidum, as divines say, when each and all were jointly and severally the efficacious moral or physical cause of the whole damage; for we are bound to make reparation for the damage which we have caused, and for that alone. This will be the case under the - following circumstances: (az) When the action of each and all is the necessary and sufficient cause of the whole damage. This condition is fulfilled when one commands or counsels an unjust act and another in consequence performs it.
(6) When the action of each is sufficient to cause the damage, and it has an actual effect in producing it, though the effect would have been produced without it. Thus if two men inflict fatal wounds on another, each is responsible for his death and all losses necessarily connected with it. In the same way, when several conspire together to commit an injury, and mutually encourage and assist each other to inflict it, all are bound jointly and severally to make restitution, (c) When the action of each is necessary for the production of the effect, so that it could not be produced without it, though the action of each would not be sufficient by itself, all are bound jointly and severally to repair the injury. Thus if two thieves carry off a safe which they could not carry alone, each in the other’s default must make good the whole damage.
When several acting together, but without mutual conspiracy in the strict sense, inflict injury on another, divines are not agreed as to whether each and all are bound to make reparation for the whole damage. Each is certainly bound to repair the damage due to his personal action, but probably be may be excused from restoring more than is equivalent to the damage which he actually caused. Thus, though those responsible for an unjust war are bound to make compensation for all the unjust damage which it causes, yet the private soldiers are only bound to make restitution for the damage which they personally cause. In the same way, if a crowd damage the property of an obnoxious political opponent, individuals who formed the crowd will only be obliged to make good the damage which they severally caused. Similarly, if injustice be done by picketing in a strike, the leaders will be bound to make reparation for all the injuries inflicted; the men who take part in it may be excused if they contribute their quota.
p. i, 274–276