Question Third. On Restitution Because of Unjust Damaging

453. 1. Unjust damaging here is understood as damage unjustly inflicted on the neighbor in external goods, without profit being taken from it. Damage can be inflicted on the neighbor in two ways: positively, by destroying his good, or negatively, by impeding him from obtaining a good (n. 429), or by not guarding goods which had to be guarded by duty of office.

2. For estimating the quantity of restitution to which he is bound who impeded another from obtaining a good, the damage which this one suffered must be considered. Therefore where the injured person had full certitude of obtaining the good, the whole good must be restored; but where he had only a more or less probable hope of obtaining the good, only a part of the good must be restored according to the value of the hope as determined by prudent judgment: for hope, however great, scarcely has half the value of the thing itself, because hope can fail and be impeded in many ways.