The accepted method of textual criticism, in…

The accepted method of textual criticism, in both theory and practice, has been to correct the text (i.e., the text of the last printed edition) codicum et ingenii ope; i.e., with the aid of the manuscript and printed sources and the critic's own ingenuity.

Divination is subordinated to authority, and any reading found in a manuscript or printed text is accounted superior to any conjecture, whatever its intrinsic merits.

The first important departure from this pattern is seen in the edition of Catullus by Joseph Justus Scaliger (1577), in which the possibilities of the genealogical method, already understood in principle by Politian and other Renaissance scholars, are exemplified by the demonstration that all the extant copies derive from a lost manuscript, whose orthography and provenance Scaliger is prepared to reconstruct.

Scaliger's greatest work is the Opus de emendatione tempore (1583; “Study on the Improvement of Time”), a study of previous calendars.

In it he compares the computations of time made by the various civilizations of antiquity, corrects their errors, and for the first time places chronology on a solidly scientific basis.

Scaliger proposes a period of 7,980 years of numbered days to be used in determining time elapsed between various historical events otherwise recorded only in different chronologies, eras, or calendars.

The length of 7,980 years is chosen as the product of 28 times 19 times 15; these, respectively, are the numbers of years in the so-called solar cycle of the Julian calendar in which dates recur on the same days of the week; the lunar or Metonic cycle, after which the phases of the Moon recur on a particular day in the solar year, or year of the seasons; and the cycle of indiction, originally a schedule of periodic taxes or government requisitions in ancient Rome.

The epoch, or starting point, of 4713 BC is chosen as the nearest past year in which the three cycles began together.

The son of Italian physician and philosopher Julius Caesar Scaliger, who had immigrated to Agen in 1525, Joseph had entered school at Bordeaux and quickly proved himself an extraordinarily precocious student.

He had gone to Parisin 1559 to study Greek and Latin and then began to teach himself Hebrew, Arabic, Syrian, Persian, and the principal modern languages.

He had converted to Protestantism in 1562 and set out on travels to French and German universities and to Italy to study its antiquities.

After the Massacre of St. Bartholomew's Day (August 1572) and the persecution of French Protestants, he had gone to Geneva, where he taught at an academy, returning to France in 1574.