The Nature of the Physical World

Summary

The Nature of the Physical World is Arthur Eddington's account, for general readers, of what relativity, thermodynamics and quantum theory had done to the picture of the physical world, and of what that picture leaves room for in human experience. It is substantially the Gifford Lectures he gave at the University of Edinburgh from January to March 1927, published in 1928 by Cambridge University Press and Macmillan. The library stores no text of the book and gives no quotations: although the work is now in the public domain in the United States, no verified transcription has been attached here, so the record describes it in its own words. The Introduction sets out Eddington's famous two tables: the familiar table of everyday life, solid, coloured and substantial, and the scientific table, mostly empty space sparsely scattered with electric charges moving at great speed. Physics, he argues, now deals only with the second, a world of symbols. Chapters I to III explain the downfall of classical physics, the special theory of relativity, and the relativity of simultaneity, with examples such as the shrinking of a moving rod and the slower clocks of a fast traveller. Chapter IV, The Running-Down of the Universe, gives the second law of thermodynamics the supreme place among the laws of nature, illustrates entropy as a measure of random shuffling, and introduces the phrase time's arrow for the one-way direction that entropy gives to time; it also offers the image of monkeys at typewriters to show how improbable an un-shuffling would be. Chapter V asks how the sense of becoming in consciousness relates to this arrow. Chapters VI and VII present Einstein's law of gravitation and its explanation as the curvature of space-time, and Chapter VIII considers man's place among the stars and the vastness of the universe. Chapters IX to XI explain the old and new quantum theory, Heisenberg's uncertainty principle and the building of the world out of relations. The last chapters turn to philosophy. Pointer Readings argues that physical science knows only the readings of instruments and their mathematical relations, not the intrinsic nature of what is measured; Reality suggests that the stuff of the world may be mind-stuff, known to us directly only in our own consciousness; Causation argues that the new indeterminism removes the physical objection to free will; and Science and Mysticism defends religious experience as a legitimate approach to an aspect of reality that physics, by its method, leaves out. The book was a best-seller and helped shape public discussion of science and religion between the wars.

Top Lessons

• What physics measures

  Eddington's two tables and his chapter on pointer readings argue that physics describes the measurable structure of things, not what they are in themselves. This does not make science false; it marks its boundary. The lesson is to distinguish what a method can know from what it cannot.

• The arrow of time

  In Chapter IV Eddington finds the direction of time not in the laws of motion, which run equally well backward, but in the growth of entropy. A shuffled pack does not unshuffle itself. He coined the phrase time's arrow for this one-way direction, and the idea remains central to physics and its philosophy.

• Freedom and the new physics

  Eddington argues in Chapter XIV that quantum indeterminism removes the claim that physics proves every human act predetermined. He does not say physics proves freedom, only that it no longer forbids it. Philosophers and scientists have disputed whether chance at the atomic level bears on human choice at all.

• Science and the spiritual world

  In Science and Mysticism, Eddington, a Quaker, holds that the methods of physics are designed to leave out the inner life, and so cannot pronounce against religious experience. He presents mystical insight as a different approach to reality, not a rival theory of atoms. Readers have found the argument either liberating or too modest.

Verified Quotes

Medical Lens

The book contains no medicine, but its later chapters bear on the mind-body problem as it stood for psychiatrists and physiologists of the interwar period. Eddington argues that physics knows matter only as structure and that consciousness is the one place where we meet the intrinsic nature of anything; he also discusses whether the indeterminacy of atomic events could matter for processes in the brain. These are philosophical proposals, and their bearing on neuroscience was disputed at the time and since.

• Chapter XIII (Reality)

  Eddington proposes that the stuff of the world is of a mental character, known directly only in consciousness.

• Chapter XIV (Causation)

  Discussion of indeterminism, the brain and free will.