IN 1772, Samuel Johnson, having completed work on his final edition of his Dictionary of the English Language, wrote a poem in Latin on the topic ''Know Thyself.'' In it he confronts the person he has become and the person he is all too likely to become. Not having the panaceas bestowed upon the modern consumer of self-help psychology nonbooks, Johnson measured himself against one of his own heroes, the humanist scholar Joseph Scaliger (b. 1540). The comparison, doubtless appropriate, was not reassuring. It was suggested by the fact that the great Scaliger had himself written a dictionary - an Arabic one - but had then gone on to greater things. Johnson, having reached his 66th year, with the essays, the edition of Shakespeare, and Rasselas behind him, had only the dictionary to show for a long life of desultory application (desultory to him), and he was afraid of the future yawning before him.
So who was Joseph Scaliger, and why did Johnson think of him in his effort to come to grips with his own personal situation? Anthony Grafton, a professor of history at Princeton University, has written the first of a two-volume critical biography that promises to help us fill in this little gap in literary history. Of course, it was not his purpose to do only that; Joseph Scaliger is one of the great scholars and, as Grafton's readable and exact book shows, an exceedingly interesting man.
Scaliger was an original. With full faith in his ability to establish accurate texts for ancient authors, he managed to leave his stamp on many of the classics to this day. Grafton clearly cares about his subject and about making him available to intelligent general readers as well as scholars. Scaliger translated the texts from the ancients and balanced the technical discussion - fascinating as a record of a fusion of rational and rhetorical method - with absorbing discussions of the disputes, characteristic of national awakening, between scholars from opposing parts of Europe.
Scaliger's great achievement, according to Grafton, was his demonstration that the ancient works on which he spent his passionate life were not ''given out by a beneficent God to the virtuous Jews and Egyptians and Druids of the world's beginning, and then corrupted over time. Rather, they were the product of history itself. They came into being only as the result of trial and error.'' Thus Scaliger may be credited with refuting ''one of the great cliches of Renaissance culture.''
And with supplying Samuel Johnson with a worthy master. It is a measure of Johnson's own greatness that he measured himself against so great a man.