Is Foreseeing Harm the Same as Intending It?

Knowing that an action will cause harm is not the same as making the harm one's purpose. In the Summa Theologiae, Aquinas discusses self-defence as an act with two effects: preserving one's life and the death of the attacker. The former may be intended while the latter falls outside the intention. What later became known as the doctrine of double effect developed this distinction into a test: harm that is foreseen as a side effect may sometimes be permitted, while the same harm deliberately used as a means to a good outcome may not be.

Suppose a rescuer breaks a locked garden gate to reach an unconscious person. The damage is a foreseen side effect of the rescue. If the gate is broken simply to punish its owner, however, the damage is the aim. The physical result may look the same, yet the reason for acting and its moral acceptability differ.

Still, “I didn't mean it” is not a moral exemption. Accounts of double effect normally also require the act itself to be acceptable, the harm not to be the means of securing the good result, the benefit to be proportionate, and no less harmful practical alternative to be available. Critics also note how easily a real intention can be redescribed as a side effect. My judgement is that the distinction between intention and foresight matters because it identifies what an agent built into the plan. Responsibility must nevertheless also consider risk, necessity, alternatives and repair, rather than being settled by an inward declaration alone.

https://www.newadvent.org/summa/3064.htm
https://plato.stanford.edu/entries/double-effect/