CH. V. LANGLOIS & CH. SEIGNOBOS

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CONSTRUCTIVE REASONING
Incompleteness of the facts yielded by documents—Cautions to be observed in filling up the gaps by reasoning	252
The argument from silence—When admissible	254
Positive reasoning based on documents—The general principles employed must enter into details, and the particular facts to which they are applied must not be taken in isolation	256
CHAPTER IV
THE CONSTRUCTION OF GENERAL FORMULÆ
History, like every science, needs formulæ by which the facts acquired may be condensed into manageable form	262
Descriptive formulæ—Should retain characteristic features—Should be as concrete as possible	264
Formulæ describing general facts—How constructed—Conventional forms and realities—Mode of formulating an evolution	266
Formulæ describing unique facts—Principle of choice—"Character" of persons—Precautions in formulating them—Formulæ describing events	270
Quantitative formulæ—Operations by which they may be obtained: measurement, enumeration, valuation, sampling, generalisation—Precautions to be observed in generalising	274
Formulæ expressing relations—General conclusions—Estimation of the extent and value of the knowledge acquired—Imperfection of data not to be forgotten in construction	279