670 THE AMERICAN JOURNAL OF SOCIOLOGY
success which the method of monographs contains remain sterile, or become even harmful, if they are not fertilized by the supreme virtue for the observer : respect for the truth.
The method of observation for the student who carries not in him this sacred respect is like logic for the sophist ; it may, in hands little conscientious, become an instrument of error and of corruption.
However, in the subject-matter of social science, observation, applied to permanent facts, offers guaranties of correctness which do not exist in pure reasoning applied to the variable facts of private or political life. A population badly observed preserves in itself all the elements of a decisive counter inquiry. The error propagated through ignorance or bad faith can always be refuted through means of a monograph due to the inquiries of a true student.
III.
I. Methods of obtaining information. There are three methods which share the favor of monograph writers ; they are : the question blank (le questionnaire}, the account book (le livre de compte), and oral questioning (I'enquete orate).
(1) The question blank method puts questions to correspond- ents who undertake to answer them. In use for a long time, this method was improved and codified by the international congress of statistics held in Brussels in 1853. It is a very convenient method since it reduces the work of the observer to the redac- tion of questions and the abstracting of replies ; but its scientific value is unfortunately quite inferior to its practical convenience, and, in spite of the numerous precedents which this method can invoke, we are forced to express the most formal reservations as to the quality of the results to be expected from it.
(2) The method of account books seems free from the objec- tions which that of question blanks incurs. The instrument of observation is this time the account book kept by a good housewife. It is this method which was used by one of the great masters of statistics, the learned Dr. Engel, for his great inquiry into the budget of European laborers. He presented
