In this first episode Bettany investigates the revolutionary ideas of Karl Marx.

Born to an affluent Prussian family, Marx became an angry, idealistic radical, constantly on the run for his political agitating and incendiary writing.

In Paris he first formulated his explosive analysis of capitalism and its corrosive effects on human nature. In Brussels he co-authored the Communist Manifesto with Frederick Engels. In London his obsessive theorizing dragged his family into poverty, and tragedy.

Marx's masterpiece Das Capital was largely overlooked in his lifetime, and only 11 people attended his funeral. Yet his ideas would generate one of the most influential, and divisive ideologies in history.

Drawing on expert opinion, and new evidence, Bettany reveals the flesh-and-blood man and his groundbreaking ideas.

Historian Bettany Hughes retraces the lives of three great thinkers whose ideas shaped the modern world.

This time she travels to Vienna on the trail of Sigmund Freud - the father of psychoanalysis.

Freud's influence surrounds us today. We take it for granted that we should be able to talk openly about our deepest feelings, from sexual difference to our inner demons. Plus phrases such as the Oedipus Complex, repression and wish fulfillment have become part of our everyday language.

Yet Freud's career was riven with controversy. His early research into cocaine almost ruined his reputation, and his theories about childhood sexuality have been fiercely debated.

Freud was a pioneer in the study of the human mind. Working as a young doctor in the 1880s, he became fascinated by the medical conundrums of nervous conditions like hysteria.

Believing these illnesses had deep-seated psychological causes, his psychoanalytic talking cure addressed deep-seated emotional issues that had seldom been discussed openly before.

Freud believed that psychoanalysis and dream-analysis could reveal hidden aspects of the mind. It's from Freud that we get the idea of the unconscious mind, where repressed emotions, irrational primal desires, and complex feelings about our parents bubble beneath the surface of consciousness.