arnaldo momigliano

The whole modern method of historical research is founded upon the distinction between original and derivative authorities. By original authorities we mean either statements by eye-witnesses, or documents, and other material remains, that are contemporary with the events which they attest. By derivative authorities we mean historians or chroniclers who relate and discuss events which they have not witnessed but which they have heard of or inferred directly or indirectly from original authorities….This distinction between original authorities and non-contemporary historians became the common patrimony of historical research only in the late seventeenth century.
—  Arnaldo Momigliano, in “Ancient History and the Antiquarian,” Journal of the Warburg and Courtauld Institutes 65, 2002 (p. 286)