This is volume No. 3 in an interesting series of reprints and translations of psychology classics which is being issued from Johns Hopkins University. The book is primarily of historical interest, De Biran having had a well-defined place in the development of psychology and philosophy in France. This essay was written in 1803 in response to a competition announced by the Institut de France, which was to determine 'the influence of habit on the faculty of thinking; or, in other words, to show the effect produced by the frequent repetition of the same operations upon our intellectual faculties'. In an introduction by Professor George Boas, of the Johns Hopkins University, the later development of thought from de Biran to Bergson is traced.