When philosophy helped me through an emotional crisis in my late teens and early twenties, I became fascinated by how ideas invented over 2,000 years ago can still save lives today. I set out on a five-year journey to find out how people from all walks of life are using ancient philosophy to withstand crises, overcome adversity and build better lives.

Along the way, I interviewed the founders of Cognitive Behavioural Therapy (CBT), Albert Ellis and Aaron Beck, and learned how they had been inspired by ancient philosophy and turned it into an evidence-based science. I met the director of the US Army’s ambitious new resilience programme, which uses techniques from philosophy to teach every American soldier inner strength. I met cops, gangsters, politicians, anarchists and astronauts, and heard how philosophy transformed their lives.

And I traveled to modern philosophical communities built around millennia-old ideas: Epicurean communes, Stoic gatherings, Sceptic summer camps, Cynic occupations, even a Platonic sect whose members include the actor Hugh Jackman. I looked at the challenges of trying to build strong ethical communities without them turning into cults.

I also explored how classical ideas of the good life are at the heart of a new ‘politics of well-being’, in which governments try to guide their citizens towards happiness and fulfilment. In the book, I warn against trying to fit an entire society into one philosophy of the good life, arguing instead that Socrates and his descendants didn’t come up with one definition of the good life, but several.

Philosophy for Life and Other Dangerous Situations is so far published in 19 countries.  It has been #1 in Amazon.co.uk’s philosophy chart, a Guardian Books bestseller, and a Times book of the year.  It presently has a 4.1 rating on Good Reads after 1245 votes, and a 4.7 rating on Amazon.co.uk after 137 reviews. The book helped to inspire the Radio 4 series, My Life As A Philosopher, which I co-presented.