14-05-2025
Thought experiment 11: The Harmless Torturer
Illustration by Marie Montocchio / Ikon Images
'Do not walk on the grass,' requests the sign on an exquisite landscaped garden. If everyone ignored this sign, the garden would be ruined. But suppose, under the cover of darkness, I strolled across it. Nobody would ever know, and I would make no perceptible difference to the lawn. So what harm would I cause?
The brilliant and eccentric Oxford ethicist Derek Parfit had as fertile an imagination for thought experiments as any philosopher of the past century. 'Derek specialised in discovering deep puzzles in philosophy – he produced problems that remain very difficult to resolve,' says the philosopher Jeff McMahan. One of those problems is the 'Harmless Torturer', from his 1984 masterpiece Reasons and Persons. It addresses the moral conundrum of actions with imperceptible effects.
Imagine a torturer and a victim. The torturer turns a dial from one to 1,000 on the pain-o-meter, thus causing the victim immediate and agonising pain. Obviously wrong. Now imagine a variation.
A thousand torturers have a thousand victims. At the start of each day, each of the victims is already feeling mild pain. Each of the thousand torturers turns a switch a thousand times, at ten-second intervals, on some instrument. Each turn of a torturer's switch affects that torturer's particular victim's pain in a way that is imperceptible. But, after each torturer has, in just under three hours, turned his switch a thousand times, he has inflicted severe pain on his victim.
Let's call these 1,000 sadists 'Gradual Torturers'. Obviously, they have acted reprehensibly. But why? Suppose they're all arrested. At trial, the prosecuting barrister could put the case that each time the Gradual Torturers turned the dial they harmed their victims, because suffering can be made imperceptibly worse. The judge may be sceptical and think: how can pain be worse if the person in pain isn't aware that it's worse?
The barrister might try another tack. Even though each turn of the dial wasn't bad, 1,000 turns of the dial was very bad indeed, because after 1,000 turns each victim certainly felt the change. That's why the behaviour of the Gradual Torturers is appalling.
He inserts 'Harmless Torturers' who differ from the Gradual Torturers, as they don't each have one victim:
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Each of the thousand torturers presses a button, thereby turning the switch once on each of the thousand instruments. The victims suffer the same severe pain. But none of the torturers makes any victim's pain perceptibly worse.
Don't we want to say that the Harmless Torturers have behaved as appallingly as the Gradual Torturers? The result has been identical: 1,000 victims ended up with the same unbearable degree of pain. But the prosecuting barrister can no longer argue that each torturer has made the life of one victim perceptibly worse. No Harmless Torturer has made any perceptible difference to any one victim. The issue of their actions must be explained in another way. As Parfit puts it: 'If we cannot appeal to the effects of what each torturer does, we must appeal to what the torturers together do.'
An action is wrong, in other words, if it's part of a set of actions that together are wrong. 'Parfit's solution is not uncontentious,' says McMahan. Is the torturer who twists the dial from zero to 1,000 – thus causing excruciating pain to one victim – really not doing anything worse than the torturer who turns it from zero to one, with an undetectable impact, on 1,000 victims? Part of the problem is whether harms and benefits should be considered 'aggregative'. Do 1,000 mild headaches equate to one life-threatening illness? Do harms just add up? And can harms be balanced, on one side of a moral equation, with benefits on the other?
Many philosophers have addressed the aggregative problem. In another example (not Parfit's), an engineer, whose job it is to transmit the World Cup to billions of football supporters, falls under the transmitter, experiencing regular, electric shocks. We could save him from the pain by cutting wires, causing a break in the TV broadcast for half an hour. Here, one man's suffering seems to outweigh the viewing pleasure of billions.
Fun intellectual puzzles, but so what? Well, take an individual's contribution to climate change. It might be convenient for me to leave a light on, and the effect on climate change of my decision will be negligible. But is leaving lights on wrong? Or consider a vegetarian's approach to meat. Whether or not an individual chooses to eat meat won't lead to the maltreatment or killing of one less animal. So, although the Parfit thought experiments are wacky, says McMahan, 'they are ubiquitous in various forms in real life'.
[See also: Thought experiment 10: The Trolley Problem]
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