Dr Bartels and Dr Pizarro knew from previous research that around 90% of people refuse the utilitarian act of killing one individual to save five. What no one had previously inquired about, though, was the nature of the remaining 10%.

Neither Barack Obama nor John McCain, however, addressed the question of whether prolonged solitary confinement is torture. For a Presidential candidate, no less than for the prison commissioner, this would have been political suicide. The simple truth is that public sentiment in America is the reason that solitary confinement has exploded in this country, even as other Western nations have taken steps to reduce it. This is the dark side of American exceptionalism. With little concern or demurral, we have consigned tens of thousands of our own citizens to conditions that horrified our highest court a century ago. Our willingness to discard these standards for American prisoners made it easy to discard the Geneva Conventions prohibiting similar treatment of foreign prisoners of war, to the detriment of America’s moral stature in the world. In much the same way that a previous generation of Americans countenanced legalized segregation, ours has countenanced legalized torture.

At this point, the impatient reader will interject that something else — something understandable and anodyne — is driving the increasing attention to food in our day: namely, the fact that we have learned much more than humans used to know about the importance of a proper diet to health and longevity. And this is surely a point borne out by the facts, too. One attraction of macrobiotics, for example, is its promise to reduce the risks of cancer. The fall in cholesterol that attends a true vegan or vegetarian diet is another example. Manifestly, one reason that people today are so much more discriminating about food is that decades of recent research have taught us that diet has more potent effects than Betty and her friends understood, and can be bad for you or good for you in ways not enumerated before.

All that is true, but then the question is this: Why aren’t more people doing the same with sex?

There was, however, a hitch. People accustomed to working for subsistence reacted in an unexpected way to higher wages. Once they earned enough for food, shelter and clothing, they felt satisfied, and they quit to enjoy their leisure, which was, after all, a novelty to most of them. It had to be taken away if capitalism was to grow at top speed. What if people were given motives to buy luxuries – things they didn’t absolutely need? Then no one would ever feel content. Who would eat with a pewter spoon if he could aspire to a silver one? Who would wear linsey-woolsey if she could toil a few hours longer and buy silk? Work could again be endless.

But luxuries are not a matter of life and death, and they left room for a new kind of doubt. Freed from absolute necessity, the growing middle classes were able to consider work for its own sake. Was it good in itself? If it seemed tedious, was a nicer spoon sufficient compensation?

A growing subculture has a fluid morality and a disdain for pretty much everyone else online.

Our sense of the preciousness of other people is connected with their power to affect us in ways we cannot fathom and in ways against which we can protect ourselves only at the cost of becoming shallow. There is nothing reasonable in the fact that another person's absence can make our lives seem empty. The power of human beings to affect one another in ways beyond reason and beyond merit has offended rationalists and moralists since the dawn of thought, but it is partly what yields to us that sense of human individuality which we express when we say that human beings are unique and irreplaceable. Such attachments, and the joy and the grief which they may cause, condition our sense of the preciousness of human beings. Love is the most important of them.