The dog I had as a kid, Snoopy, had a talent for football and for chewing my stuff. This included assaulting my refractor telescope at regular intervals, though poor Snoopy was typically the loser in those battles. In truth, suburban Liverpool was not the greatest place for amateur astronomy and I was driven to observe other objects of heavenly beauty (God bless you, Mrs Mills, at no. 23) and develop interests that didn't depend on cloudless night skies. In reading about the history of science, my heroes became Kepler, Galileo and Einstein, figures whose bodies ate, slept and stumbled but whose intellects wheeled through farthest space and penetrated into the deepest heart of nature.

This fascination with reconciling the routines of the everyday with the immensities of the universe has never faded. Nor has the idea that the two converge through quite simple, almost childlike, questions. What would it be like to travel on a wave of light? Such elementary queries inspired the teenage Einstein, hiking through the Apennine mountains, and never left him alone thereafter. It is surely similar puzzles that bring us all to our passions, to enthusiasms we cannot stop exploring without becoming what Weber labelled a ‘specialist without spirit’.

It is this fascination that drives me to write about philosophies and theories of social policy. I define the subject broadly, to encompass social relations, political governance, cultural identities and popular discourses that others might locate in alternative disciplines. But such matters do not affect the journey that lies before us, or the childlike questions I am still impelled to raise. On what grounds can our liberty be legitimately restricted? To what extent should individuals be protected from themselves?

We are therefore going to ask normative questions – ‘what should we do and why?’ – and to this end we will be playing with some of the most fundamental building blocks of inquiry. In British railway stations, it is common to hear announcements such as the following: ‘We apologise for the late departure of the 10.23 to Kettering; this was because of delays to the incoming service’. Why was the outgoing train late? Because the incoming train was late! We cannot be satisfied with such circular explanations, especially given their frequent occurrence in public and political life.