Since I got involved in a research project on childhood obesity, I’ve encountered some unexpected philosophical questions. I was asked to take part in this project because of my interest in ethics and politics. These are topics we explore in a new book, Childhood Obesity: Ethical and Policy Issues, and I’ll say a few words about our broad approach below. But here I’d like to focus on some traditional philosophical questions about knowledge and reason that this research has highlighted for me.

Reason, doubt, and knowledge

Epistemology is the area of philosophy that concerns knowledge – its nature and its limits. Even basic claims, such as how widespread childhood obesity is, pose epistemological questions. News headlines are full of statistics, and hardly a day goes by without another story about how different foods or behaviours affect our health. Working with scientists and statisticians, I’ve seen how hard it is to gather and interpret evidence. How can we really know what children eat on a daily basis, or how their body size compares with that of children 10 or 20 years ago? We need to piece together a picture from many different sorts of none too certain evidence.

These epistemological worries aren’t quite the same as Descartes’ in the Meditations (1641) – that we might be experiencing a mere dream, or that an evil demon might be deceiving us. But like Descartes, I think scepticism is still essential – not just about the headlines, but also the carefully researched papers in the scientific journals. Over the last century, philosophers of science have explored how the scientific process is very different from the results published in textbooks. It often takes decades of hard work to achieve a fair degree of scientific certainty. In the meantime, science involves a lot of trial and error; opposing claims and criticisms are essential. There is no such thing as a scientist who’s always right, or a research project that reveals the whole truth.

Descartes pictured an individual who knows – and doubts – alone. Science shows us how wrong this picture is: people gain knowledge together. Knowledge isn’t threatened by total, paralysing, individual scepticism (am I dreaming everything?!). Nor is it guaranteed, as Descartes went on to suggest, by our idea of a benevolent God who would not deceive us. Instead, knowledge is secured by raising and addressing individual doubts. In other words, exposing errors and increasing knowledge is a collective activity. And we shouldn’t see scepticism and knowledge as opposites: scientific progress grinds to a halt where people claim total certainty.

Reason, uncertainty, and action

This poses a practical question: how should we act in the face of uncertainty? Although we often use Cartesian scepticism to introduce our subject, modern philosophers don’t tend to take it very seriously. This is mainly because no one could think or act without accepting some claims about the world around him or her. I may doubt what a particular scientist claims (is it really true that children get x% less physical activity than they used to, for example?). But if she and I didn’t share many similar beliefs about the world, we couldn’t have a meaningful disagreement about this. In fact, I would argue, we couldn’t do anything together. (Discuss!)

Still, we have to accept that many beliefs we share are fuzzy round the edges. But is uncertainty a reason not to act? Human beings have always had to live with uncertainty. It’s not certain that I’ll be run down by a car if I walk into the road – and it’s not certain that I’ll be safe if I stay on the pavement. Still, I know enough to minimise the risks. Of course, childhood obesity is more complex. It’s easy to stay on the pavement, but not so obvious what society or individuals should do to reduce obesity rates. (Some people think they know – ‘Just eat less and exercise more!’ But one thing we do know from the science is that it’s just not that simple.)

This brings me to a thought about human reason. Some philosophers argue that reason tells us to maximise a single good, such as happiness or welfare. But although it’s easy to say how to avoid some sorts of misery, it’s never proved possible to tell people how to maximise happiness. In my view, reason really shows its power when we deal with many different things and face up to uncertainty about how to achieve each of them. As we stress in our book, reducing obesity can’t be our only goal. We have to do many things – for example, educate children, keep them safe, and give them enough freedom to learn about personal responsibility. (Never mind what adults want too.) There’s lots of room for uncertainty about how to do all these things, and doubtless we often get it wrong.

Above, I suggested a very different picture of reason and knowledge than Descartes’: Reason is the power to hold many different sorts of evidence in mind, to entertain doubts and respond to criticism – without succumbing to paralysing uncertainty or dreaming of a God who would never deceive us. When we decide how to act, perhaps we can think of reason in a similar way. Reason is the power to hold different priorities in mind, and to find ways of living and acting that enable us to do a passable – though rarely perfect! – job of addressing them all. By sharing our views and criticisms – and by accepting that certainty is not available – we can nonetheless find ways to think and act reasonably. 

What do you think? Share your comments with us below.

Dr Garrath Williams teaches on our BA Philosophy and LLM/MA Bioethics and Medical Law programmes.

• Childhood Obesity: Ethical and Policy Issues, by Kristin Voigt, Stuart G. Nicholls, and Garrath Williams, published by Oxford University Press on 25 April 2014.