Plato's great discovery was radically new but has echoed down the ages. His "theory of Ideas" has shaped the whole of Western culture and his name is known worldwide. More than 2000 years ago Plato used his "allegory of the cave" - which envisaged people looking at shadows on a cavern wall and taking them for realities - to express a terrible suspicion. He saw his fellow Athenians living in a manipulated world of appearances - cut off from reality and put to sleep by material pleasures, wealth and demagogic politicians - and hoped, with this image, to shake them out of this sleep. Plato's...

Already as a student Hegel was often reprimanded for excessive drinking and gambling and he is surely one of the most unconventional - today, one might say "coolest" - thinkers of all time. He is sometimes mockingly accused of having been drunk when he hit on his key idea of a "World Spirit." Nevertheless, his philosophy remains fascinating and highly relevant even today. Hegel was the first philosopher to realize the full implications of the dimension of "becoming." Human life has as much the character of a process as do Nature and History. A human being comes into the world as a baby and...

Albert Camus was a legend in his own lifetime, as a successful author, a philosopher and a "ladies' man." His philosophical discoveries remain provocative even today. Because, like all great philosophers, Camus posed the question of the meaning of life. But his answer to this question was an answer of an entirely new kind. This question as to the meaning of life has been answered, of course, very differently down the centuries. For Plato it is 'the Good' that holds the world together; for Hegel the 'World-Spirit'; for Marx the relations of production; for Sartre freedom; for Nietzsche 'will...

Heidegger is without a doubt one of the most important thinkers in the history of the Western world. He called his philosophy a "fundamental ontology." His interest as a philosopher extended beyond the individual sciences to the underlying question of the meaning of life as a whole. His key question, then, was: "What is the meaning of Being?" But if we are to ask about the meaning of Being, and thus about the meaning of life, we must - so Heidegger argues - first look into the question of just what kind of being it is that poses such questions. This question-posing being, he says, is Man...

Sartre is surely one of the most important philosophers of the 20th Century. His "philosophy of existence" influenced not just academic debate but the whole of Western civilization, especially European youth. In France, from the end of WW2 on into the 1960s, a certain "youth culture" milieu composed of secondary school and university students and young artists and intellectuals proclaimed their "existential" attitude to life by wearing the black clothes and horn-rimmed glasses that Sartre was seen to wear in so many photos from the period. The motto of these "existentialists" ran: 'do not let...

The Viennese physician and psychoanalyst Sigmund Freud moved from hypnotizing his patients to interpreting their dreams and discovered thereby the hitherto unexplored dimension of the unconscious mind. Each of us, argued Freud, has hidden wishes, desires, and drives which influence our actions below the level of our awareness. A great role is played here, already from childhood on, by sexual desire and pleasure. The nursing infant still lives entirely by the "pleasure principle," taking everything into his mouth, crying when he wants something, and laughing when he is satisfied. But he must...

Never before or since has a single philosopher produced such a tremendous effect as Karl Marx. His great vision of a society without private property was heeded worldwide and had huge historical effects. Allegiance to his ideas was proclaimed by revolutionaries, parties, governments and states. Marxism spread all around the globe. Marxist revolutions occurred in countries as different as Russia, China, Vietnam, Cuba, Nicaragua and Mozambique as well as many others, until at one point almost a third of humanity were living under communism. But some hundred years after Marx's death the...

It was, of all people, to a Scottish philosopher of morality that there fell the role of intellectual forefather of capitalism. It was Adam Smith who was the first to recognize and describe, in 1776, the basic principle of the market economy. His magnum opus, "The Wealth of Nations," is still looked on today as "the Bible of capitalism." And indeed, for a period of ten years it was, after the Bible itself, the most-translated book on earth. Smith created the "magic formula" of the free play of supply and demand and his theory of "the invisible hand" spread like wildfire around the world,...

Immanuel Kant is thought to be perhaps the greatest of all philosophers. And Kant did make, in the 18th Century, two great discoveries which engage us still today. Firstly, he founded the globally acknowledged 'categorical imperative' in moral philosophy; secondly, he became the first philosopher to succeed in answering that question as old as humanity of how knowledge arises in our brains. In his main work, the 1000-page "Critique of Pure Reason," Kant analysed the working of Man's thinking apparatus. He posed the critical question: what can a human being know with certainty and what can he...

Rousseau possessed a brilliant mind and one that questioned every accepted value and idea. Whatever most were "for," Rousseau was always "against" He was against monarchy, against the church, against the status quo, against inequality, against traditional education, against marriage, and (of course) against technical progress and the destruction of Nature. Today we might call Rousseau a "professional rabble-rouser." His contrariness was his trademark. He spent most of his life as a quasi-vagrant or a refugee. Sometimes it was the church, other times the government of one country or another...