Double effect

Double effect distinguishes intending harm, including harm used as a means, from foreseeing harm while pursuing a good end. Traditional formulations also require a permissible act, a sufficiently serious reason, and limits on how the good is achieved. Calling something a side effect does not alone establish permission.

Intention concerns what an agent adopts as an end or as a means of achieving it; foresight concerns what the agent expects to happen. Regretting a harm does not automatically make it unintended if the plan depends on producing it. Conversely, a foreseeable harm can remain a side effect. Traditional formulations also impose conditions on the act, the means, and proportionality. The distinction therefore offers a structured argument, rather than a general excuse for unwanted consequences.

Imagine repairing a dangerous bridge while knowing that the noise will disturb nearby residents. Compare deliberately creating that disturbance to drive residents away. The same inconvenience can occupy different roles in a plan; proportionality and less harmful alternatives still matter.

Critics ask whether intention can bear so much moral weight or be reliably distinguished from foresight. An agent may describe a plan strategically to avoid acknowledging intended harm. Applying the doctrine therefore requires examining how the plan works, what the person is committed to achieving, and whether the harm is necessary.

Use an invented infrastructure case: repairing a dangerous bridge temporarily disrupts businesses, while deliberately closing a business to pressure its owner uses that disruption as part of the plan. Similar losses could result, but the losses play different roles in the explanation of action. In either case, ask about alternatives and avoidable burdens. Even a clearly unintended cost needs justification; classifying it correctly does not finish the assessment of what the decision maker owes.