Donald Trump's election promise to make America great again seemed to tap into a belief that things were better in the past.

Is this the case, or do we have any cause for optimism?

Steven Pinker is the author of a new book called Enlightenment Now: The Case for Reason, Science, Humanism and Progress. He joined us to explain why he believes the world today is a better place than we might think, despite the negative thinking so many of us engage in.

"I argue that, inadvertently, some of the gross negativity of popular and journalistic culture paved the way for Donald Trump to say 'society is a disaster and only I can save it.' If we realised how much is actually going better, we'd be less receptive to someone saying 'only I can fix it.'"