After John McDonnell said he was still committed to the socialist transformation of Britain, we ask what that might mean. Does socialism really require the overthrow of capitalism? What's the difference between socialism and communism? And with successful Democratic candidates in the US starting to use the s-word in public, what does socialism have to offer in America? Plus we talk about whether social media and social networks offer the possibility of a new kind of socialism for the twenty-first century. With Helen Thompson, Chris Bickerton and Chris Brooke