. >> host: james barrel for nabors year chicago where booktv is on location. the newest book, warfare state. >> host: on location at the university of chicago where we're talking with several professors of university who were also authors now we're pleased to be joined by david straus, author of the living constitution and teaches law at the university of chicago law school. david strauss-kahn how do you define a living constitution? >> a good question. it is an idea that is controversial but it should be. is the idea of the constitution as it was drafted in 1787 and has been amended since then, it has said it evolves over time in order to keep up with changing circumstances and ideas about how society should be run. >> host: what do you consider a current evolution? >> guest: there are several examples but here is one. throat the first 100 years through the late 19th century, the idea was the federal government could be very small and federal and state governments could play a limited role to regulate the economy progress the country became a less agrarian th