When I was studying for my Master’s at Johns Hopkins University I had to write a paper on Kenneth Arrow’s impossibility theorem (otherwise known as ‘Arrow’s paradox’ – in the fashion of ‘Xeno’s paradox’, I suppose). Arrow, who was joint winner of the Nobel Memorial Prize for Economics in 1972 at the age of just 51, demonstrated the theorem already in his PhD thesis but went on to give it a broader audience through his Social Choice and Individual Values (1951). In a very elegant nutshell, Arrow demonstrated that democracy is impossible (you can read about his theory here). At Tim Smit’s talk (see 10 February post) I asked a question which I am (half-seriously) thinking of firming up into ‘Westlake’s impossibility theorem’. The theorem goes as follows: a) democracies are predicated on political parties seeking to gain power by aggregating a sufficient number of votes so as to win a majority; b) political parties are rational entities, which means that they will always act to maximise votes (or to minimise vote loss) for the next electoral challenge they face; c) policy choices to enhance sustainability necessarily involve benefits that will not be achieved within a single electoral cycle and costs that will be incurred within a single electoral cycle; therefore, democracy and sustainability are mutually incompatible. I rest my case. Help me out of this depressing predicament, please.