Walden or Life in the Woods by Henry David Thoreau, 1850.
To a philosopher all news, as it is called, is gossip, and they who edit and read it are old women over their tea. Yet not a few are greedy after this gossip. There was such a rush, as I hear, the other day at one of the offices to learn the foreign news by the last arrival, that several large squares of plate glass belonging to the establishment were broken by the pressure-news which I seriously think a ready wit might write a twelve-month, or twelve years, beforehand with sufficient accuracy. As for Spain, for instance, if you know how to throw in Don Carlos and the Infanta, and Don Pedro and Seville and Granada, from time to time in the right proportions - they may have changed the names a little since I saw the papers - and serve up a bull-fight when other entertainments fail, it will be true to the letter, and give us as good an idea of the exact state or ruin of things in Spain as the most succinct and lucid reports under this head in newspapers: and as for England, almost the last significant scrap of news from that quarter was the revolution of 1649; and if you have learned the history of her crops for an average year, you never need attend to that thing again, unless your speculations are of a merely pecuniary character. If one may judge who rarely looks into the newspapers, nothing new does ever happen in foreign parts, a French revolution not excepted.
The end of the quote
My questions are:
1. How I'll know when to use "need" like modal like here "you never need attend to that thing again"?
2. Is there some reason why Grammarly create red line beneath "need" like it fails and suggested 'to need'?