Johnson’s dexterity in retort, when he seemed to be driven to an extremity by his adversary, was very remarkable. Of his power in this respect, our common friend, Mr. Windham of Norfolk, has been pleased to furnish me with an eminent instance. However unfavourable to Scotland, he uniformly gave liberal praise to George Buchanan, as a writer. In a conversation concerning the literary merits of the two countries, in which Buchanan was introduced, a Scotchman, imagining that on this ground he should have an undoubted triumph over him, exclaimed, ‘Ah, Dr. Johnson, what would you have said of Buchanan, had he been an Englishman?’ ‘Why, Sir, (said Johnson, after a little pause,) I should NOT have said of Buchanan, had he been an ENGLISHMAN, what I will now say of him as a SCOTCHMAN,—that he was the only man of genius his country ever produced.’
From Boswell’s Life of Johnson.