When I first heard the allegations of serial sexual misconduct against the American folk-rock singer Ryan Adams earlier this year – that he had emotionally and psychologically abused several women and underage girls, using his status in the music industry as leverage – I didn’t want to believe it. Yet this desire to not-believe strongly preceded any acquaintance I had with the actual facts. Indeed – and as I am now ashamed to admit – I initially read the facts with great skepticism, hoping that they were wrong. Only with effort have I forced myself to put aside my initial disbelief, and consider things impartially, making a more balanced assessment. Why?

One answer comes from feminist theory. As a man who has been raised in a male-dominated society, one that tends to privilege the status and testimony of men, and to cast aspersions on those of women – most especially when it comes to issues of sex – I am ideologically conditioned to react this way. Sadly, I suspect there is much truth in this. But it is not the only explanation in play. Another consideration is that I didn’t want Adams to be guilty because I like his music. And the worry that I had – initially, without even realising it – was that, if Adams is indeed guilty, then I won’t be able to enjoy his music any more. And I don’t want that to be the case. Hence, I initially read the accusations against Adams with skepticism, precisely because I (subconsciously) wanted to protect my future enjoyment of his records.

It is not uncommon to find that one’s enjoyment of something is irrevocably damaged if that thing turns out to be closely connected to somebody who has committed serious wrongs. Many people will now feel deeply uncomfortable watching films associated with Harvey Weinstein. Similarly, critically acclaimed movies starring Kevin Spacey – even if made long before any accusation of wrongdoing was levelled against him – will no longer seem the obvious choices for Saturday night viewing that they once were. And this is not simply because we want to take a moral stand against Weinstein or Spacey (though that might certainly be true). It is because we feel that the films themselves are tainted.

But this is odd. A film or TV show, after all, is a thing ultimately independent of the private actions of the actors or producers who happened to help make it. And yet one seems to bleed inexorably into the other. Once you know the charges levelled against Weinstein, you can’t simply carry on watching his films as you did before. The same, I fear, will be true of Adams’s music if it turns out that he is as bad as they say. Many people are currently experiencing precisely such anxiety regarding the music of Michael Jackson, given the latest and most distressing of the allegations made against him.

What is going on here? It is not simply the old, harsh truth that good things can come from bad people. By all accounts, the 18th-century philosopher Jean-Jacques Rousseau was a pretty unpleasant character. He fell out with everybody, let down most of those who trusted him, and thought it fit to write a book on education despite abandoning many of his own children to orphanages. On the other hand, he was the author of some of the greatest works of philosophy ever written. Similarly, according to the Pulitzer-winning biography The Years of Lyndon Johnson (1982) by Robert A Caro, the 36th president of the United States was a bullying, lying, power-crazed sociopath, who literally stole a Senate election on his way to the highest office. Then again, Johnson also passed the Civil Rights Act.

Life is complicated; not all good things harmonise.

The fact that good things can come from bad people is a separate issue from the fact that knowledge of somebody – or something – having done a bad thing can deeply affect how we view the status of the thing itself. Take a simple but effective example, borrowed from the philosopher Simon Blackburn’s recent paper on this topic. Imagine I invite you over to dinner and, while carving the roast, I casually mention that this is the very knife that the assassin used to murder my wife and children. Would you still be comfortable eating the slice of beef I’ve just plopped on to your plate? And it can work in the other direction, too. Imagine I have a room filled with 20 Fender guitars. I tell you that you can have any of them you like – but one of them was the very guitar that Jimi Hendrix used during his last performance! I bet I know which one you’ll pick, whether you want to keep it for yourself or quickly take it to auction.

Sometimes our feelings over these matters can run very high indeed, becoming full-blown moral sentiments. Imagine a sailor who, shipwrecked and clinging to a plank for three days, finally washes up on shore. Yet the first thing he does is burn the plank that saved his life. Does he not seem to do something wrong? Or consider the case of a man whose son is killed by a motorcyclist, who is sent to jail but remains in possession of the motorbike. After being released, the motorcyclist begins riding the bike again. But the father, outraged, takes a sledgehammer to the vehicle. Prosecuted for criminal damage, the father is given only a negligible sentence by the judge. We all understand why – and we approve.

Indeed, for many centuries, English common law recognised the category of the ‘deodand’, or an object that was implicated in a human death, such as a cart, a boat, a stone or a tree. The deodand had to be forfeited to the authorities, and its value would then equal the compensation awarded by the courts to the victims’ families. But this practice was abolished in the 1840s, when railway companies lobbied hard to stop their expensive steam trains being used to set the value of awards in the growing number of train-fatality cases. Although this particular compensation mechanism is no longer legal practice, the basic idea of the deodand still makes sense to us.

The assassin’s knife is still perfectly good as a knife. Why be so upset about my using it tonight?

Yet, when you think about it, this is rather strange. After all, it is simply a matter of luck that these particular objects have these particular histories. The assassin could well have used her own knife, or picked a different knife from the drawer. But she picked this knife – and so this knife is now the one that disturbs us. Hendrix (let us suppose) could have picked any of the available Fenders in the shop that day, he just happened to favour that one – and so now that one is special. The examples of Adams, Spacey and Weinstein fit the pattern, too. How come we extend our discomfort backwards, to cover artistic products associated with them from a time when they themselves were not (let us suppose) morally compromised? Weinstein is only one producer among many in Hollywood. Why is his financing of a film once upon a time – when it could easily have been someone else – enough to make us dislike that film today?

This is genuinely puzzling. After all, the job of a knife is simply to cut things. The knife that the assassin used is still perfectly good as a knife. So why be so upset about my using it tonight? Likewise, The Usual Suspects (1995) did not suddenly become a worse film – indeed, it didn’t change at all – the moment the accusations against Spacey were made public. So why not re-watch that old DVD when you get home? The Hendrix guitar is (let us suppose) no better as a guitar than any other that Fender produced that year; they all sound roughly the same when played well. So why is Hendrix’s guitar special? It seems rather mysterious.

Why does bare luck make such a difference to how we feel? Are we simply irrational when it comes to such matters? Perhaps not – and perhaps because asking about whether it is rational for us to have these luck-dependent aversions and attractions is not the right way to think about what is going on.

The best discussion of why we react in these varying – and perplexing – ways comes from the 18th-century Scottish Enlightenment thinker Adam Smith. Nowadays much more likely to be known (somewhat misleadingly) as the ‘father of economics’, Smith was employed as professor of moral philosophy at the University of Glasgow for around 12 years, and hence spent much of his time teaching and writing on such matters. Indeed, his first book – The Theory of Moral Sentiments (1759) – puts forward not just the earliest sustained discussion of the issue of what philosophers now call ‘moral luck’, but one of its most compelling evaluations.

Smith’s discussion didn’t just cover objects or people, and the taint that can be associated with them because of their good or bad histories. It also covered the irregularity of our responses to outcomes that are heavily affected by luck. Imagine the following case: I carelessly throw a brick off the top of a building, but fortunately it doesn’t hit anybody, and shatters harmlessly on the pavement below. You’re likely to think that I’m a bad and irresponsible person, and deserve to be admonished accordingly. But you’ll probably also think that the matter should end there. Now vary the scenario: imagine that the brick does hit somebody, and kills them. The likelihood is that you will now think that I deserve much more in the way of blame, and indeed of punishment. (Prison seems a perhaps not unreasonable response.)

Let us suppose that my motivations – eg, sheer indifference to the safety of others – and my actions – chucking a brick without looking – are identical in both cases. Why, Smith asked, do we feel that the latter is so much worse than the former? It was, after all, simply a matter of luck that somebody walked along at that precise moment, got hit by the brick, and died. (It works in the other direction, too: we would surely feel it too harsh to send a person to prison simply because the brick might have hit a passerby, when in fact it didn’t.)

The underlying intention determines whether we approve of an act, not its consequences alone

Yet this kind of scenario led to a puzzle. Smith thought it undeniable that we assess the morality of actions not by their actual consequences, but by the intentions of the agent who brings them about. To see that this is indeed true, consider the following example. Imagine that you see me rescue a cat from a tree. When I get to the ground, the cat wriggles free and scurries away. Assuming that my intention was to save the cat, you’ll likely think that I did a good thing. But what if you now find out that my intention was to barbeque the cat for dinner? In both cases, the consequences are the same – the cat is brought down from the tree, wriggles free, and runs away. Yet your evaluation of the morality of the act will shift markedly once you learn of my culinary intentions. Try any example you like, and you’ll get the same result: it’s the underlying intention that determines whether or not we approve of an act, not the consequences of the act alone.

For Smith, it is a truism that we assign different moral weight to intentions, not to consequences, and one that nobody will deny, at least when it comes to philosophical theory. Nonetheless, in practice, we often find ourselves heavily swayed by consequences even when, on the face of it, those consequences shouldn’t matter. Take the brick-throwing example again. In both cases, my intention was bad, because in throwing the brick I showed callous disregard for the safety of others. In theory, then, I am equally culpable whatever the outcome, at least if intentions are supposed to be what counts. But, in practice, we feel far more strongly in the case where the brick does hit somebody. So consequences do matter after all – even though moral philosophers tend to think that it’s only intentions that should matter.

For this reason, Smith thought that our moral sentiments in such cases were ‘irregular’. Why do we respond so differently to consequences that have bad outcomes, when those outcomes are purely a matter of luck? Smith confessed that he did not know why we are psychologically rigged up this way. Here he hit what he took to be explanatory bedrock, and simply assigned this ‘irregularity’ to the workings of ‘nature’, for which he could give no further explanation. (We, living after Charles Darwin, might want to posit an evolutionary story – but that was something Smith had no access to.) Nonetheless, Smith was confident that, although he could not explain why we are like this, on balance we should nonetheless be grateful that we are indeed rigged up this way.

The first reason Smith gave for why it is good that we are this way is that if, in practice, we really did go around judging everybody solely by their intentions, and not by the actual consequence of their actions, life would be unliveable. We would spend all our time prying into people’s secret motivations, fearing that others were prying into ours, and finding ourselves literally on trial for committing thought crimes. This, Smith thought, might be appropriate for God at the final judgment – but it would be hell on Earth if applied to mortal justice.

Second, it is quite useful that we generally tend to be bothered about actual consequences, rather than just underlying intentions. It’s all very well and good if you intended to get me a birthday present – but if you didn’t actually manage to do so, my gratitude is markedly lessened. This will seem somewhat unfair if the reason you didn’t get me a present is because you fell grievously ill. Your intention, after all, was good. It will seem much less unfair, however, if the reason is simply that your desire to sit around watching Netflix in your underpants was stronger than your desire to go to the shops. We tend to be both more grateful for good consequences and more resentful about bad ones, which is clearly socially useful. On account of the fact that you have to actually do the good thing to get the praise – and equally, you have to actually do the bad thing to get the punishment – people are more likely to follow through on their good, and not act upon their bad, intentions. This is a highly welcome feature of social existence, all things considered.

The ‘irregularity’ of our sentiments encourages us to respect the sanctity of other persons

Finally, and perhaps most interestingly of all, Smith thought that there was a special effect of the ‘irregularity’ of our sentiments: it predisposed us to be careful around other people. One last example: imagine you are walking along a path above a cliff, and you accidentally dislodge a boulder, which crashes down and kills the rock-climber below. You didn’t mean to do this – it was an accident! But the fact that you did do it matters enormously. You will be blamed by others, and will likely blame yourself too. (‘Why didn’t I look where I was going?!’) But the fact that we feel ourselves responsible even for the things that we didn’t mean to do is, Smith thinks, a very useful and desirable state of affairs, insofar as it encourages us to take care when we are acting in ways that could (inadvertently) harm others. Precisely because you know you’ll rightly be held responsible for the death of people below you, even if you only accidentally knock a rock onto them, you’re more inclined to take care where you tread when you go for a clifftop stroll. As Smith put it, the ‘irregularity’ of our sentiments in this regard encourages us to respect the sanctity of other persons:

The happiness of every innocent man is, in the same manner, rendered holy, consecrated, and hedged round against the approach of every other man; not to be wantonly trod upon, not even to be, in any respect, ignorantly and involuntarily violated, without requiring some expiation, some atonement in proportion to the greatness of such undesigned violation.

What has this got to do with the assassin’s knife, the guitar used by Hendrix, or the films that Spacey starred in? Like Smith, I cannot explain why our psychologies tend to transfer the guilt of an agent, or the history of what an object was used for, on to the past or future status of a thing itself. They apparently just do. But following Smith, this seems to be a very desirable state of affairs, one that we should not want to do without. It is good that we feel aversion to artifacts (be they physical objects, films, records or whatever) associated with sex crimes, murders and other horrors – even if this is a matter of sheer luck or coincidence – because this fosters in us not only an aversion to those sorts of crimes, but an affirmation of the sanctity of the individuals who are the victims of them. In turn, that makes most of us less likely to engage in evil acts ourselves. Perhaps even more importantly, it makes us less likely to remain indifferent even when we are not ourselves directly affected by injustices perpetrated against others. Instead, we come to see innocent people as sacred, and to be protected from the predations and depredations of those who would harm them. In this way, our moral world is more tightly knitted together.

As Smith was at pains to point out, we are psychologically complex creatures, capable of sharing each other’s emotions, and forming intricate moral bonds accordingly. Sometimes that process can get messed up, working itself out back to front – as, for example, when I reflexively take the side of Ryan Adams because I like his music and want to protect my future enjoyment of it. (Fortunately, this sort of back-to-front reaction can be corrected by reflection, at least by those willing to undertake it.) But, typically, the process works for the greater good. A world in which people did not recoil in horror at my use of the assassin’s knife to carve dinner, or in which watching The Usual Suspects was not considered a suspect choice in light of the allegations against Spacey – such a world would certainly be a worse place.

In all of this, there is an important lesson for moral philosophy. For some time now, ethical theory has been dominated by two rival camps. Consequentialists, who think that morality is primarily about maximising some approved set of outcomes, and deontologists, who think that morality is primarily about rules, duties and obligations. These two opposed outlooks, with all their innumerable variations, have been duking it out for well over a century. But neither can make much sense of the importance of anything that has been written above. And yet, the cases of ‘moral luck’ that I have discussed are not minor side issues, or trivial diversions, but go to the heart of our everyday, as well as some of our deepest moral experiences. Adam Smith saw this very well. We stand to learn a great deal from his emphasis not on calculating consequences or fulfilling obligations, but on human psychology and the moral sentiments that structure our ethical lives.