At the heart of it is simply: What do we do at this stage in human history as human beings? Humanity has to address the greatest threat that it has ever known, which is climate breakdown.
The "truth of climate breakdown" filtering through to ordinary people is driving the effectiveness of Extinction Rebellion, one of its senior figures has said.
Jamie Kelsey Fry, 54, said a steady drip of warnings in recent years has made citizens serious about taking direct action, with many of the group's members first-time activists.
The Extinction Rebellion (XR) spokesman told the Press Association: "You might call it visceral politics. It's a visceral reaction. Either you stand up now and you're on the right side of history or you're not.
"I've just been on Waterloo Bridge this morning with five old-age pensioners, all retirees, all grandparents, and they've never done anything like this before.
"Yet they feel absolutely compelled to stand up for the sake of their children. I think the United Nations saying we've got 12 years left has really alarmed a lot of people.
"But alongside that there are stories coming in daily like the iceberg twice the size of New York about to break off from the Antarctic.
"So not only is the sort of truth of climate breakdown and the emergency filtering through to everyday people but also the fact that it's happening a lot more quickly than any of the scientists feared."
Mr Kelsey Fry, a former school teacher and contributing editor to the New Internationalist magazine, said it was "absolutely" the group's intention to keep up protests in London for two weeks.
He claimed around nine out of 10 people were supportive of their traffic-blocking protests. Mr Kelsey Fry said: "We really do apologise for putting ordinary people out from their daily routine but there is no option left for us.
"Every other option that has been tried over the past three decades has not worked - marching from A to B, writing letters to MPs, giving money to NGOs, none of that has worked.
"At the heart of it is simply: What do we do at this stage in human history as human beings? Humanity has to address the greatest threat that it has ever known, which is climate breakdown."
Thomas Hornall is a reporter with Press Association.