A Treatise Concerning the Principles of Human Knowledge

Summary

George Berkeley's Treatise Concerning the Principles of Human Knowledge, published in Dublin in 1710 when its author was a twenty-five-year-old fellow of Trinity College, argues that the material world, understood as an unthinking substance existing outside every mind, is a philosophers' invention. What exists are minds and the ideas they perceive; for sensible things, to be is to be perceived. The book's subtitle announces its target: the causes of error in the sciences and the grounds of scepticism, atheism and irreligion. A short Preface asks the reader to suspend judgment until the whole has been read. The Introduction, in twenty-five numbered sections, attacks the doctrine of abstract ideas, especially John Locke's account of a general idea of a triangle that is neither oblique nor rectangle, neither equilateral nor scalene, but all and none of these at once. Berkeley says he cannot frame such an idea. A word becomes general, he argues, by standing as a sign for any of many particular ideas, and language serves ends besides conveying ideas, such as stirring the passions. Philosophers have raised a dust of words and then complained that they cannot see. Part I, in 156 sections, builds the positive case. The objects of knowledge are ideas of sense, of reflection, and of memory and imagination, and there is something distinct from them that perceives them: mind, spirit or soul. A table exists when it is seen or felt. Berkeley turns Locke's distinction against itself: if colour, heat and taste exist only in the mind, so do extension, figure and motion, for no one can conceive the one set without the other. Material substance as a support of qualities proves either contradictory or empty. Ideas are passive; only spirits act. Since the ideas of sense do not depend on my will, they must be caused by another Spirit, and the steady order in which that Spirit excites them is what we call the laws of nature. Berkeley then answers objections: that real things become chimeras, that fire would no longer burn, that we must stop saying the sun rises, that Scripture speaks of bodies. His replies insist that nothing real is lost; only a needless abstraction is removed. The closing sections draw consequences for natural philosophy, including Newton's absolute space, for mathematics and the infinite divisibility of extension, and for knowledge of other minds. God, he concludes, is known more evidently than any human being, and the aim of the whole is to promote reverence and the truths of the Gospel. Berkeley called this book Part I; a planned second part was never published. A second edition appeared in London in 1734. The library's text is the Project Gutenberg edition, which prints editorial section headings in capitals and gives some first-edition readings in notes.

Top Lessons

• Test a word by the idea behind it

  Berkeley's Introduction holds that many disputes survive only because a word appears to name something no one can actually picture, such as a triangle of no particular kind. His method is to ask, of every key term, what particular idea it calls up. Even readers who reject immaterialism can use this habit in any argument.

• Common sense can be on a strange-sounding side

  Berkeley claims that his denial of matter defends the ordinary person, who trusts what is seen and touched, against philosophers who say real things lie hidden behind appearances. He keeps the table, the apple and the fire; he removes only the unperceived substratum. The lesson is that a surprising thesis may be offered as a return to plain experience.

• Order in nature as a language

  For Berkeley the regular sequence of sensations, the laws of nature, shows the wisdom of the Spirit who produces them, and science learns to read those regularities as signs. Nature becomes something like speech addressed to finite minds. This turns natural philosophy into a form of attention to God's steady habits of acting.

• Philosophy in the service of piety

  The subtitle and the final section state that the book was written to undermine scepticism and atheism and to promote reverence for God. Berkeley's metaphysics is not a game with appearances but an argument that God is the most evident of all minds. Readers can weigh the argument while understanding the purpose that drives it.

Verified Quotes

Medical Lens

The Principles is not a medical book, but it bears on the mind-body problem that later psychiatry inherited: Berkeley denies that bodies act on minds at all and treats the perceiving spirit as the only active substance. His earlier New Theory of Vision, on how sight learns distance through association with touch, was discussed in connection with Cheselden's 1728 report of a boy given sight by cataract surgery. Late in life Berkeley championed tar-water as a near-universal remedy in Siris (1744), a separate work that belongs to the history of popular medicine rather than to this treatise.

• Part I, sections 18-20

  Berkeley argues that no one can explain how body could act on spirit to produce an idea, so material causes explain nothing about perception.

• Part I, sections 43-44

  Summary of the New Theory of Vision: distance is not seen directly but suggested by ideas of sight that have been joined with ideas of touch.