The Principles of Psychology

The Principles of Psychology

Title page from the first edition.
Author	William James
Country	United States
Language	English
Subject	Psychology
Publisher	Henry Holt and Company
Publication date	1890
Media type	Print (Hardcover and Paperback)
Pages	xviii, 1393

The Principles of Psychology is an 1890 book about psychology by William James, an American philosopher and psychologist who trained to be a physician before going into psychology. There are four methods from James' book: stream of consciousness (James' most famous psychological metaphor); emotion (later known as the James–Lange theory); habit (human habits are constantly formed to achieve certain results); and will (through James' personal experiences in life).

The openings of The Principles of Psychology presented what was known at the time of writing about the localization of functions in the brain: how each sense seemed to have a neural center to which it reported and how varied bodily motions have their sources in other centers.

The particular hypotheses and observations on which James relied are now very dated, but the broadest conclusion to which his material leads is still valid, which was that the functions of the "lower centers" (beneath the cerebrum) become increasingly specialized as one moves from reptiles, through ever more intelligent mammals, to inhumans while the functions of the cerebrum itself become increasingly flexible and less localized as one moves along the same continuum.

James also discussed experiments on illusions (optical, auditory, etc.) and offered a physiological explanation for many of them, including that "the brain reacts by paths which previous experiences have worn, and makes us usually perceive the probable thing, i.e. the thing by which on previous occasions the reaction was most frequently aroused." Illusions are thus a special case of the phenomenon of habit.

In the use of the comparative method, James wrote, "instincts of animals are ransacked to throw light on our own...." By this light, James dismisses the platitude that "man differs from lower creatures by the almost total absence of instincts". There is no such absence, so the difference must be found elsewhere.