4. Personal philosophies

Reading the recently released letters from Freud’s first love Martha, we can meet Freud the proto-psychoanalyst, treating his sweetheart with clinical precision (she sent him a lock of her hair; he asked whether her hairbrush had torn it out) but also encouraging her to talk about her feelings.

Nietzsche had appalling eyesight – one of the reasons his philosophy is delivered in pithy aphorisms: bite-sized philosophy that was dangerously appealing to the Third Reich.

Marx was afflicted – probably from his twenties – with a debilitating skin disease; doctors argue this may have fed his sense of ‘alienation’.

5. Why we need to care today

Marx’s economic analysis might be flawed but it identified the crucial issue of alienation from what he calls ‘our species essence’ – the danger of becoming a cog in a vast capitalist machine.

Nietzsche brilliantly prophesied a ‘health and safety’ culture where, in the absence of God, we would seek the religion of comfortableness. He questioned the disastrous consequence of focusing on reward in the afterlife but reminds us that without a higher Divine purpose (Nietzsche proclaimed that God was dead) we would be liberated, or condemned, to create our own value systems.

Freud’s acceptance of the normalcy of abnormal encouraged toleration, while his rubric to identify and to pursue our desires was used as the basis of US advertising culture.

6. Marx would have been condemned by Marxist regimes and Nietzsche by the Nazis

Millions have been killed in the name of Marxism yet the terrible irony is that Marx would have been condemned by rigid Marxist regimes. Despite his grandstanding statement, ‘communism is the riddle of history solved’, Marx thought we should never stop questioning orthodox ideas.

In Nietzsche’s notebooks, where the thinker sketches out his infamous ‘Will to Power’, a shopping list – toothpaste, buns, shoe polish - has been scrawled over the work-in-progress, yet this text was misappropriated as a foundational truth of Nazi dogma.

All three philosophers remind us of the danger of ideas calcifying into ideologies, that with great ideas comes great responsibility, and that the written word, as Plato said, ‘is often an orphan’ and can be wilfully abused.

The word ‘man’ comes from the Proto-Indo European ‘manu’ – a mind. As a species we are defined by our power to think.

Marx, Nietzsche and Freud throw down a challenge: The future of the world is not down to ‘them’, but ‘us’; we have a social duty to use the power of our minds to work out how best to live, and the point of our lives.