¹ Foot, P., Virtues and Vices and Other Essays in Moral Philosophy (Berkeley and Los Angeles, 1977), p. 26Google Scholar. The distinction leaves us with some difficult cases. Suppose a potential killer and an unloaded gun are in a room. Rather than removing the gun, I load it and put it back where it was. Arguably, this does not fall into Foot's first category, because there is no sequence in train which will lead to the shooting of the killer's victim, and which I decline to intervene in by loading the gun. Nor, however, does the case fall clearly into Foot's second category: I do not simply remove an obstacle – the gun not being loaded – that is holding back a train of events resulting in the killing.

² Rickless, S. C., ‘The Moral Status of Enabling Harm’, Pacific Philosophical Quarterly 92 (2011), pp. 66–86, at 66Google Scholar, characterizes enabling harm as ‘withdrawing an obstacle that would, if left in place, prevent a pre-existing causal sequence from leading to foreseen harm’. On this approach one cannot enable unforeseen harms (nor allow them). This epistemic clause is not part of Foot's characterization of enabling harm. Foot's use of the terms ‘thought of’ and ‘as it were’ in the quoted passage suggests that she takes series of events that allow and enable outcomes to differ, not in respect of intrinsic features of the events, but in how we think of them. I set aside this interpretation of Rickless's view.

³ In this article, I simply criticize the moral equivalence thesis. Its falsity is compatible with one of the more complicated answers, so for all I say here those answers remain on the table.

⁴ Vihvelin, K. and Tomkow, T., ‘The Dif’, Journal of Philosophy 102 (2005), pp. 183–205, at 194CrossRefGoogle Scholar.

⁵ Barry, C., Øverland, G., ‘The Feasible Alternatives Thesis: Kicking Away the Livelihoods of the Global Poor’, Politics, Philosophy and Economics 11 (2012), pp. 97–119CrossRefGoogle Scholar; Barry, C., Lindauer, M. and Øverland, G., ‘Doing, Allowing, and Enabling Harm’, Oxford Studies in Experimental Philosophy, ed. Knobe, J., Lombrozo, T. and Nichols, S. (Oxford, 2014), pp. 62–90CrossRefGoogle Scholar.

⁶ Hanser, M., ‘Killing, Letting Die and Preventing People from Being Saved’, Utilitas 11 (1999), pp. 277–95CrossRefGoogle Scholar; Rickless, ‘The Moral Status’.

⁷ For the notion of interaction between morally relevant factors, see Dancy, J., Moral Reasons (Oxford, 1993)Google Scholar; Kagan, S., ‘The Additive Fallacy’, Ethics 99 (1988), pp. 5–31CrossRefGoogle Scholar; Kamm, F. M., ‘Killing, Letting Die: Methodological and Substantive Issues, Pacific Philosophical Quarterly 64 (1983), pp. 297–312CrossRefGoogle Scholar; McMahan, J., ‘Killing, Letting Die, and Withdrawing Aid’, Ethics 103 (1993), pp. 250–79CrossRefGoogle ScholarPubMed, at 274).

⁸ Some deontologists think that doing and allowing (as opposed to, say, intending and merely foreseeing) harm are morally equivalent, and that in principle a consequentialist can affirm that doing harm has greater negative value than allowing harm.

⁹ Thomson, J. J., ‘A Defense of Abortion’, Philosophy and Public Affairs 1 (1971), pp. 47–66, at 47–9Google Scholar.

¹⁰ Kamm, F. M., Bioethical Prescriptions (Oxford, 2013), p. 187CrossRefGoogle Scholar.

¹¹ For an account along these lines, see Kamm, ‘Killing’. For critical discussion, see Kagan, S., The Limits of Morality (Oxford, 1989)Google Scholar.

¹² It should be noted, however, that in his arguments against the moral equivalence thesis Rickless seems to presuppose that the distinction between doing and allowing has moral significance. Accordingly, he cannot (nor does he) employ the moral equivalence thesis to undermine the moral asymmetry between doing and allowing harm.

¹³ Pogge, T., World Poverty and Human Rights: Cosmopolitan Responsibilities and Reforms (New York, 2008), p. 23Google Scholar.

¹⁴ Barry and Øverland, ‘The Feasible’, p. 112.

¹⁵ Barry and Øverland, ‘The Feasible’, p. 110.

¹⁶ Barry and Øverland, ‘The Feasible’, p. 113.

¹⁷ This is compatible with the possibility that the acts differ contingently in other, permissibility-relevant, dimensions in a way licensing us to say that, in those dimensions, the worse action is better than the less bad action.

¹⁸ Rickless, ’The Moral Status’, p. 66; see also Scanlon, T., Moral Dimensions (Cambridge, 2008), pp. 3, 102–5CrossRefGoogle Scholar.

¹⁹ See Bennett, J., The Act Itself (Oxford, 1995), pp. 62–73Google Scholar; Barry et al., ‘Doing’.

²⁰ McMahan, ‘Killing’, pp. 263–4.

²¹ Rickless, ’The Moral Status’, p. 73.

²² We can set aside John Taurek-like reasons for doubting the permissibility of allowing harm to a few to save the many based on the notion that each person should be given a fair chance (whatever that is) of being saved. See Taurek, J., ‘Should the Numbers Count?’, Philosophy and Public Affairs 6 (1977), pp. 293–316Google ScholarPubMed.

²³ Obviously, the argument is not deductively valid, nor does Rickless claim that it is. It strikes me as a plausible inference to the best explanation, though, for reasons set out below, ultimately I think it is unwarranted.

²⁴ This is true even if we compare cases where Sally has promised not to enable/allow harm to the respective jumpers – more harm can permissibly be imposed on Sally by the recipient of the promise to avoid the bad consequences of Sally's breaking her promise by enabling harm than that which can permissibly be imposed on Sally by the recipient of her promise, i.e. to the relevant jumper, to avoid the bad consequences of her breaking her promise not to allow harm. In Burning Building 3 and the variations of it which I consider Sally has not issued any such promises to the persons involved; nor has she otherwise communicated to them that they can rely on her acting in a certain way.

²⁵ Cf. McMahan, ‘Killing’, p. 255. The findings of Barry et al., ‘Doing’, suggest that most people take agents who knowingly enable harm to have stronger compensatory duties to victims than agents who knowingly allow harm. (Strictly speaking, they use various test cases where the agent is innocent because she is unaware of the harm she countenances. Arguably, this is not the best way to test the significance of innocence, because one can be culpably negligent in bringing about a harm one was not aware that one might bring about.) On the assumption that, generally speaking, there is a connection between the stringency of compensatory duties to victims and the amount of harm a potential victim can impose on a potential harm-doer to avoid harm, these findings provide some support for my claim about our relevant moral intuitions here. (Admittedly, Barry et al., ‘Doing’, p. 83, think that the compensatory duties of agents who unknowingly enable harm are less stringent than the compensatory duties of agents who unknowingly do harm. Even if this is right, and right because compensatory duties of agents who unknowingly enable or allow harm are morally on a par, this does not rescue the moral equivalence thesis. Enabling and allowing harm would still interact differently with knowledge of the harm one countenances in relation to duties of compensation, and thus in this way they are morally inequivalent.)

²⁶ Cf. Barry et al., ‘Doing’, p. 82. This suggestion is similar to Kamm's observation that in James Rachels's pair of examples of the uncle countenancing his nephew's drowning (which Rickless appeals to) one is entitled to harm the uncle to prevent the nephew from drowning in the doing-case in ways that do not translate to the allowing-case. See Rachels, J., ‘Active and Passive Euthanasia’, New England Journal of Medicine 292 (1975), pp. 78–80Google Scholar.

²⁷ Cf. Boorse, C. and Sorenson, R., ‘Ducking Harm’, Journal of Philosophy 115 (1988), pp. 115–34, at 115–17CrossRefGoogle Scholar.

²⁸ Barry et al., ‘Doing’, p. 65.

²⁹ I am grateful to Susanne Burri for input at this point.

³⁰ It makes no important moral difference to my assessment of this pair of cases whether Sally is aware of the jumper's beliefs. However, an anonymous reviewer found the example more convincing with this stipulation. Moreover, an experiment conducted by Barry et al., ‘Doing’, shows that in cases of enabling harm many do think it makes a moral difference to compensatory obligations whether the agent of enabling harm is aware of the consequences of what she is doing (see n. 26). Because I only need to identify one case where allowing and enabling harm interact differently with expectations in order to defeat the moral equivalence thesis, I have no reason not to make this stipulation.

³¹ The claim that enabling and allowing harm interact differently with reasonably formed beliefs upon which persons threatened with harm act is compatible with the following claim: that an agent has a duty to make some effort to avoid causing others to form and act upon reasonable but false beliefs about what he will allow to occur. Presumably, such a duty is less stringent than the similar duty to prevent others from reasonably forming, and then acting upon, false beliefs about what he, the agent, will enable.

³² The moral difference between the two cases cannot be explained by the expectations of the two sets of jumpers because the jumpers do not differ in this respect: both expect to be rescued by the net if they jump. It might be replied that their expectations do differ in one respect: the lone jumper expects that Sally will not enable her to be harmed, while the pair of jumpers expect that Sally will not allow them to be harmed. However, if the difference between these two expectations is morally significant, the best explanation of it is that the difference between enabling and allowing harm is morally significant. From what else could the moral significance of the distinction derive?

³³ This applies even if the two people act on the reasonably formed belief that Sally would not allow them to die.

³⁴ Allowing and enabling harm also interact differently with malicious intentions. Rickless, ‘The Moral Status’, p. 71, accepts that our ‘intuitions . . . count as evidence for the claim that malicious harmful enabling is morally equivalent to harmful doing’. However, given that malicious harmful allowing is not morally equivalent to harmful doing it follows, pace Rickless, that allowing and enabling harm are not morally equivalent. To see that malicious harmful allowing is not morally equivalent to harmful doing consider a variation of an example provided by Jeff McMahan which Rickless, ‘The Moral Status’, p. 70, discusses in this context. A person is trapped atop a burning high building. Fortunately, there is a self-standing net below. Unfortunately, the wind will blow it away before the person reaches the ground if he jumps. This person's enemy is present at the scene and could prevent the net from being removed by the wind, but refrains from so doing out of malice. Here the trapped person could not, say, permissibly shoot his enemy if doing so would make the enemy collapse in front of the net, thereby preventing it from being blown away from the building. However, he could permissibly use lethal force in a comparable case of doing harm (e.g. to prevent someone from setting the building on fire thereby trapping him with no means of escape).

³⁵ Thomson, J. J., ‘Killing, Letting Die and the Trolley Problem’, Rights, Restitution, and Risk: Essays in Moral Theory, ed. Parent, W. (Cambridge, MA, 1986), pp. 78–93Google Scholar; cf. Hanser, ‘Killing’, p. 286 n. 10. An exception is Thomson, J. J., ‘Turning the Trolley’, Philosophy & Public Affairs 36 (2008), pp. 359–74CrossRefGoogle Scholar; see, however, FitzPatrick, W. J., ‘Thomson's Turnabout on the Trolley’, Analysis 69 (2009), pp. 636–43CrossRefGoogle Scholar. However, while Thomson now thinks it is impermissible to divert the trolley thereby killing one and saving five, it seems that this judgement on her part is not a moral intuition, but a theory- or argument-generated view.

³⁶ For present purposes I need not identify what these features are. All I need to deny is (1) that the features are common to all cases of enabling harm and allowing harm, on the one hand, and some cases of doing harm, on the other; and (2) that this explains why enabling and allowing harm are morally equivalent and morally less wrong that harming. In support of this denial (of (1), specifically) consider a case where I enable someone else to kill a third person by giving him a gun without which he would otherwise have been unable to kill. This is a case of enabling harm that is no less wrong, morally, in virtue of having trolley-like features.

³⁷ Boorse and Sorenson, ‘Ducking’, p. 127; Vihvelin and Tomkow, ‘The Dif’, p. 196.

³⁸ Rickless, ‘The Moral Status’, p. 78.

³⁹ Hanser, ‘Killing’, p. 285.

⁴⁰ Hence, I disagree with Rickless when he writes: ‘So if harmful enabling were morally equivalent to harmful doing, then the DDA [i.e. the doctrine of doing and allowing: KLR] would speak against his moving his car. Drive Away 2 therefore suggests that harmful enabling is morally equivalent to harmful allowing, rather than to harmful doing’ (Rickless, ‘The Moral Status’, p. 78). The conditional in the first sentence is false, because DDA does not apply, or at least does not apply in the right way, to trolley-like situations.

⁴¹ E.g. F. Howard-Snyder, ‘Doing vs. Allowing Harm’, Stanford Encyclopedia of Philosophy, <http://www.plato.stanford.edu/entries/doing-allowing/> (2011), p. 2.

⁴² Rickless, ‘The Moral Status’, p. 79.

⁴³ See Foot's examples of enabling reported above in section I.

⁴⁴ Rickless, ‘The Moral Status’, p. 79; cf. Vihvelin and Tomkow, ‘The Dif’, p. 194.

⁴⁵ Rickless, ‘The Moral Status’, p. 80; see also p. 83. One would like to ask: ‘Completely stable with regard to what?’ The answer cannot be that it is completely stable with regard to the survival of the innocent person. There is no causal sequence already in train whose continuation will result in the victim's death in the absence of intervention by any agent. Moreover, if this were the answer the situation would also be completely stable in Burning Building 3.

⁴⁶ McMahan, ‘Killing’, p. 257.

⁴⁷ This is unlike McMahan's version of the case, where the Dutch boy seems to make continuous efforts to keep his finger in the crack. My version shows that if something counts as withdrawing, (a) the provider of the obstacle must do something in order to prevent the removal of the obstacle, and (b) it must cost the one who put it there in the first place something not to withdraw the obstacle. Note also that this case is one in which the situation is, in some sense, completely stable. No intervention by any agent is needed to prevent the dyke from cracking. Yet it does seem to be a case of enabling harm if the Dutch boy withdraws his finger.

⁴⁸ Consider a case where, to prevent the dyke from being washed away, the Dutch boy places his finger in the crack. This does not completely stop the destruction of the dyke, but it slows it down very considerably. Now suppose that after some time, the boy decides to withdraw his finger, and that in the process of doing so, inevitably, he will damage the dyke in such a way that the destruction is accelerated (relative to the situation before his intervention). Suppose that given the time he has already spent with his finger in the crack, and given the accelerated rate of destruction after his withdrawal, the dyke will break at exactly the same time it would have broken had he never intervened in the first place. Will it still count as enabling harm now if he withdraws his finger? Would it do so if he were to accelerate the rate of destruction so much that the dyke will break before it would have done had he never intervened in the first place?

⁴⁹ Bennett, The Act, p. 68.

⁵⁰ It might be replied that the situation cannot go on indefinitely. However, if this is the relevant criterion hardly any situation is completely stable.

⁵¹ McMahan, ‘Killing’, p. 274.

⁵² Previous versions of this article were presented at the University of Oslo, 19 June 2012; the University of Roskilde, 5 April 2013; and the Society for Applied Philosophy Conference, University of Zurich, 29 June 2013. I thank Christian Barry, Saba Bazargan, Susanne Burri, Tom Douglas, Matthew Hanser, Ingmar Persson, Thomas Søbirk Petersen, Rob Reich, Samuel Rickless, Jesper Ryberg, Alex Voorhoeve, Garrath Williams, Gerhard Øverland, and an anonymous reviewer of this journal for excellent comments and criticisms.