Being a self-sacrificing soul I recently enrolled myself in a critical piece of public health research: I gave up alcohol for January. If appetite is the new front-line in health, if our desires are becoming the death of us, then self-restraint must be the new penicillin, and, to squeeze the analogy a little, the Petri-dish is any human heart. Just how difficult could it be to up-end the glass for a month?

For the first ten days I was almost beatific. I drifted through the days serene as a barefoot Buddha. If these were the fruits of self-denial, give me more. I felt like I was being cleansed, as if I were shucking the heaviness of Christmas. After all, how many of those many, many glasses of wine did I really enjoy?

About day twelve I went to a talk with a friend. We met in a bar and later went for dinner.  Where children drove me to steady drink, for my friend it was being a GP. She had a pint of cold, cold lager. Mine was a cola. Be nice to have a beer I thought. She had a second. Be nicer still I thought to have another. We went for food. Hers a sauvignon blanc, mine a cola. Nicer by far would be a glass of wine. Still, there were compensations: the late walk back home from the tube; the foxes; the cold air; the bare trees against the winter sky, how fresh they were, how keen.

At the weekend my in-laws came to stay. Over dinner they sank several bottles with their daughter. I stretched out a pomegranate cordial. The drunk can drive you to drink. How else to tolerate them? By ten-thirty I had done the washing up and was in bed, reading de Quincey.

The barefoot Buddha upped and left. A fortnight in, delight had congealed into sulky irritation. And then my mind divided. One side, call him Good, was intent on seeing it through. His serpentine twin however was open to offers. Virtue is its own reward said Good. Forget feast and famine said Bad, little but often wins the day. To his aid came that old necromancer the BMJ – weekend bingers in Belfast did worse than the persistent French it screamed. Dinner times were tricky. Across the table the Light of My Life, ample glass in hand, ‘beaded bubbles winking at the brim, and purple-stainèd mouth’ busily distilled a host of temptations. Bad mind had a field day. What about Isaiah Berlin’s bent twig he hissed? (Unfortunately he had misspent as much of his youth reading as Good, albeit with an eye on different passages.) An appetite long held down will spring back with renewed vigour. True Berlin was talking about German nationalism, not alcoholism, but the principle surely held. What harm a glass or two?

Public health policy properly focuses on the health of populations. Its field of study is humankind writ large: social gradients, transport policies, the food and drinks industries, the ‘obesogenic environment’; the things outside of us that determine how healthy we are. But critical as these are, when it comes to appetite they can only ever be part of the picture. Overwhelmingly, the new public health problems involve human choices.  For as long as we remain the sort of things we seem to ourselves to be they will involve inner struggle. Liberal utilitarianism, the ordinary language of public health ethics, is notoriously shy of these problems. Harm to others notwithstanding, a liberal state, so the mantra runs, should be neutral as to the lifestyle choices of its citizens, and woebetide a moralising politician. But what to do when the public cost of choice heads for the ceiling?

As I wrestled with my thirst, of necessity I moved from a public language to one more private. The abstract messages of public health gave way to an inner tussle between appetite and will, between what immediately I wanted and what, all things considered, might be better for me. It is a moral tussle in its way of course, a struggle to define the good life and to secure the inner resources to pursue it.

Liberal states can struggle to bring these public and private languages into synch. The private sphere is the arena of individual autonomy, and in this sphere our moral choices are a matter for ourselves alone. The public sphere creates the minimum rules to ensure one person’s choice is compatible with the equal exercise of choice for others. But the rising problems of public health require a straddling of these domains, and liberal discomfort is palpable. This is why we are hearing more about nudging, about incentives, about the science of human motivation. It also helps explain the temptation to smuggle in moral judgements under guise of neutral science, why values can masquerade as biological data, why health can often seem like the only human good.

It is sometimes said that these problems present a limit-case for liberal theory, that they cannot be addressed within the prevailing political paradigm. Either the self is regnant in the private sphere or it is wholly enchained. But the opposition is a false one. What is needed surely is more sophisticated debate about what we mean by personal autonomy.  Autonomy is not the mindless exercise of freedom. It is not merely about an unlimited scope of choice. Our autonomy depends upon a host of duties, duties to others of course, but also, and critically in terms of health, duties to ourselves, howsoever difficult it may be always to fulfil them.

Julian Sheather is ethics manager, BMA. The views he expresses in his blog posts are entirely his own.