Thomson’s Other Method of Trolley Cases

The controversy over how, if at all, discoveries in moral psychology are relevant for ethics rages on without much attention to leading ethicists’ arguments. (And many people taking this course may not be familiar with ethics.) We will therefore first consider an argument from Thomson and then attempt to find ways in which discoveries in moral psychology might be relevant.

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Notes

It is harder to see how discoveries in moral psychology might be undermine or support ethical principles if we turn from Foot to Thomson.

Why bother? Those who, like Kant, deny that discoveries in moral psychology are relevant for ethics are unlikely to accept Foot’s method of trolley cases (as outlined in Foot and Trolley Cases: Kant Was Wrong) or Kamm’s approach to arguing that distance can be ethically relevant (see Singer vs Kamm on Distance). We can establish a stronger conclusion about moral psychology’s relevance if we take Thomson’s argument as our starting point.

Thomson against Foot

Thomson (1976) aims to show that Foot is wrong about the trolley problem. But what is this problem?

‘why is it that Edward may turn that trolley to save his five, but David may not cut up his healthy specimen to save his five? I like to call this the trolley problem, in honor of Mrs. Foot’s example’ (Thomson, 1976, p. 206).

Foot (1967) suggests that it is at least in part because duties not to harm rank above duties to help (see Foot and Trolley Cases: Kant Was Wrong). To counter this suggestion, Thomson adds a further trolley case:

‘Frank is a passenger on a trolley whose driver has just shouted that the trolley’s brakes have failed, and who then died of the shock. On the track ahead are five people; the banks are so steep that they will not be able to get off the track in time. The track has a spur leading off to the right, and Frank can turn the trolley onto it. Unfortunately there is one person on the right-hand track. Frank can turn the trolley, killing the one; or he can refrain from turning the trolley, letting the five die’ (Thomson, 1976, p. 207).

Frank’s case is constructed in such a way that (according to Thomson¹) if he does nothing, he fails to help; whereas if turns the trolley, he harms one person in order to help five. His choice is between harming one or helping five. Thomson infers:

‘By her [Foot’s] principles, Frank may no more turn that trolley than David may cut up his healthy specimen’ (Thomson, 1976, p. 207).²

Thomson responds by relying on what appears to be an empirical claim:

‘Yet I take it that anyone who thinks Edward may turn his trolley will also think that Frank may turn his’ (Thomson, 1976, p. 207).

It is possible to interpret Thomson as offering this as a normative claim (anyone must take it to be so). Alternatively, she might consider her position as one that is relevant only to those who agree with her on this. So there is no obvious commitment to an empirical claim here.

In any case, Thomson takes the pattern of judgements about what David, Edward and Frank should do to justify rejecting Foot’s view³ in favour of her own:

‘what matters in these cases in which a threat is to be distributed is whether the agent distributes it by doing something to it, or whether he distributes it by doing something to a person’ (Thomson, 1976, p. 216).⁴

Distinguish Normative from Psychological Claims

We must be careful to distinguish two questions:

1. [normative] Why may Edward turn the trolley while David may not cut up the healthy human?

2. [psychological] What determines why some people judge, on reflection, that Edward turn the trolley while David may not cut up the healthy human?

As I understand Foot (1967), her method is to start from answers to the second, psychological question; use the answers to draw inferences about ethical principles; and then infer answers to the first, normative question using those principles (see Foot and Trolley Cases: Kant Was Wrong).⁵

By contrast, I can find no sign that Thomson regards the second, psychological question as relevant. She appears entirely focussed on the first, normative question.

What is Thomson’s Method of Trolley Cases?

I interpret Thomson as offering an entirely different kind of argument to Foot. Thomson relies on premises including these two:

1. There is a morally relevant difference between David and Edward.

2. There is no morally relevant difference between Edward and Frank.

How can the reader know that these premises are true? Thomson appears unconcerned with this question. (‘One’s intuitions are, I think, fairly sharp on these matters’ (Thomson, 1976, p. 207).)⁶ The premises about particular cases appear obvious to her and those around her; so perhaps it was, in 1976 at least, reasonable to start from them. They are candidates for being self-evident.

Thomson then infers, from these and other premises about particular scenarios, that her principle is more likely to be true than Foot’s principle.⁷

How Could Moral Psychology Be Relevant?

If discoveries in moral psychology could undermine our grounds for accepting that Thomson’s premises about particular scenarios (such as 1 and 2 above), then it would undermine or support ethical principles given that Thomson’s argument could work.

There is further way in which moral psychology could be relevant. To see this, consider a line of objection to Thomson’s argument:

Whether an agent distributes a threat by doing something to the threat or to a person is ethically irrelevant. Thomson’s solution to the trolley problem is therefore incorrect.

Note that this is a line of objection and but not actually an objection because the premise of the objection is unsupported. (An objection to an argument is not simply a statement contradicting its conclusion.⁸)

As a reader, I am tempted by this line of objection. Prior to reading Thomson, I assumed, wrongly, that everyone agreed with the premise of the objection. Should I be persuaded by Thomson’s argument? This depends, among other things, on whether I have stronger grounds for holding that Thomson’s proposed principle concerns an ethically irrelevant factor than for accepting her premises about moral differences between particular scenarios.⁹

Why is this relevant? Reflection on how someone might get stuck on this line of objection highlights that Thomson’s method of trolley cases relies not only on readers having grounds for accepting her premises about particular scenarios (such as 1 and 2 above) but also on these grounds not being outweighed by any grounds they have, prior to considering Thomson’s arguments, for rejecting Thomson’s conclusion.

So if discoveries in moral psychology could weaken our grounds for accepting Thomson’s premises about particular scenarios (such as 1 and 2 above), and if this made those grounds weaker then your prior grounds for rejecting Thomson’s conclusion, then it would undermine or support ethical principles given that Thomson’s method of trolley cases could work.

Conclusion

Thomson’s method of trolley cases, unlike Foot’s, is not continuous with moral psychology. It is therefore harder to see how discoveries in moral psychology could be relevant.

But reflection on how a reader could use Thomson’s argument to gain knowledge of ethical principles indicates that there are at least two possibilities.

Whether discoveries in moral psychology actually undermine or support ethical principles therefore depends on what the discoveries are and whether they can weaken someone’s grounds for accepting Thomson’s premises. Do any discoveries do this?

Glossary

References