Keynes, Hayek and Marx: Three thinkers with differing ideas about capitalism.

Masters of Money: A worthy video to spend three hours, either as refresher course or inaugural primer about three veins of economic thought.

BBC economics editor Stephanie Flanders examines how three extraordinary thinkers, Keynes, Hayek and Marx, helped shape the 20th century.

The Guardian's review of the 2012 series is here. Flanders keeps the conversation accessible, without hue and wonk.

Keynes ... capitalism is too important to be left to its own devices. 

Hayek ... capitalism only works when government leaves it to its own devices. 

Marx ... capitalism must die of its own devices.

When the facts change, do you change your mind?

This one's verified.

"When the facts change, I change my mind. What do you do, sir?"

The case of origin is at the Quote Investigator, but it's the sentiment encapsulated by the quote that has caught my attention.

Do you change your mind, or follow the lemmings off the cliff's edge?

When the Facts Change, I Change My Mind. What Do You Do, Sir?

John Maynard Keynes? Paul Samuelson? Winston Churchill? Joan Robinson? Apocryphal?

Dear Quote Investigator: John Maynard Keynes was an enormously influential economist, but some of his detractors complained that the opinions he expressed tended to change over the years. Once during a high-profile government hearing a critic accused him of being inconsistent, and Keynes reportedly answered with one of the following:

When events change, I change my mind. What do you do?

When the facts change, I change my mind. What do you do, sir?

When my information changes, I alter my conclusions. What do you do, sir?

When someone persuades me that I am wrong, I change my mind. What do you do?

Because there are so many different versions of this rejoinder I was hoping you might determine if any of them is real. Is there any truth to this anecdote?