The key ideas

A Treatise Concerning the Principles of Human Knowledge

George Berkeley, 1710

A twenty-five-year-old Irishman declared that things have no existence apart from being seen and felt. People laughed at him, but refuting him turned out to be surprisingly hard. Here is his reasoning step by step: from a triangle nobody can picture to a tree in the courtyard that nobody is looking at, and to the one who, according to Berkeley, sees it all the same.

Who it is for

For anyone who has ever wondered whether the world exists when nobody is looking at it. And for anyone who wants to understand, with no background at all, one of the boldest ideas in the history of philosophy.

We have first raised a dust and then complain we cannot see.

A kick at a stone outside the church in Harwich

In 1763, in the English port town of Harwich, two friends came out of a church. The young Scot James Boswell was sailing for Holland that day, and the writer Samuel Johnson had come to see him off. They started talking about Bishop Berkeley and his ingenious proof that matter does not exist. Boswell observed that although we are satisfied the doctrine is not true, it is impossible to refute it. Johnson struck his foot with mighty force against a large stone, so hard that he rebounded from it, and said: “I refute it thus.”

Did he? To answer, we need to go back half a century, to Dublin. In 1710 the twenty-five-year-old George Berkeley, who had entered Trinity College at fifteen and stayed on to work there, published A Treatise Concerning the Principles of Human Knowledge. The book was met mostly with ridicule.

Berkeley claimed something that sounds like madness: things have no existence apart from being perceived. Yet he himself believed he was not taking a single stone away from the world. What he took away was something else: the invisible matter of the philosophers, which nobody had ever seen or touched. And he did it to defend common sense against scepticism, the doubt that we know anything at all.

Here is his reasoning step by step: from a triangle nobody can picture to a tree in the courtyard that nobody is looking at. By the end it will be clear how the Treatise itself would have answered Johnson's kick.

The philosophers raised the dust themselves

Berkeley begins with an observation that is easy to check. Ordinary people who walk the high road of plain common sense are usually at ease. But as soon as someone starts reasoning about the nature of things, a thousand doubts spring up. The further they go, the more paradoxes they meet, until they end up where they started or, worse, in a gloomy scepticism.

The usual explanation is the weakness of reason: our minds, so the argument goes, were made to help us live, not to see into the essence of things. Berkeley disagrees. It is hard to believe that right conclusions from true principles should lead to absurdities. Nor would God have given people a strong desire to know what is bound to be beyond their reach. So the trouble is not the mind but false principles we have adopted ourselves.

Hence his best-known line from the introduction: we have first raised a dust and then complain we cannot see. Berkeley's plan is to find those false principles and clear them away. There are two main ones: the belief in abstract ideas, and the belief in a matter that exists without any perception. He starts with the first.

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About the author

George Berkeley (1685–1753) was an Irish philosopher and clergyman, later Bishop of Cloyne. He published the Treatise at twenty-five, while working at Trinity College in Dublin.

All books by this author: George Berkeley

Terms from the book

  • Johnson
  • Aristotle
  • Copernicus
  • scepticism
  • Locke
  • idea
  • Laws of nature
  • Harwich: A port town in the east of England, from which ships sailed to Holland in the eighteenth century.
  • Boswell: James Boswell, an eighteenth-century Scottish writer, friend and biographer of Samuel Johnson. His Life of Samuel Johnson is considered one of the most famous biographies in the English language.
  • Trinity College: The oldest university in Ireland, founded in Dublin in 1592. Berkeley entered it at fifteen and later taught there.
  • Abstract idea: In Locke's view, a general idea the mind gets by leaving out everything particular, for example the idea of a triangle in general. Berkeley held that we have no such ideas.
  • Schoolman: A scholar of medieval school philosophy, which relied on the authority of Aristotle and church teaching. In Berkeley's time the word was often used as a reproach for empty disputes.
  • Esse est percipi: Berkeley's Latin formula: “to exist is to be perceived”. It applies to the things we see and feel, but not to minds themselves.
  • Spirit: For Berkeley: that which perceives ideas and acts, that is, the mind, the soul or the self. Unlike ideas, a spirit is active.
  • Primary qualities: Extension, figure, motion, solidity and number. Philosophers before Berkeley held that these exist in things themselves.
  • Secondary qualities: Colour, sound, taste, smell, heat and cold. These were thought to be mere sensations in the mind, caused by particles of matter.
  • Substratum: A foundation, a bearer of qualities. Philosophers used the word for the matter that supposedly “supports” the qualities of things.
  • Matter: In the Treatise: an unthinking and unperceived foundation of things, existing outside any mind. It is the existence of this that Berkeley denies, not the existence of stones and trees.
  • Limerick: A comic poem of five lines with a particular rhyme scheme, popular in English verse.
  • Atheism: The denial that God exists. Berkeley believed that belief in matter was its main support.

All terms

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