In summary: Wikipedia)But the term 'Unitarian' was not formally used until the 1690s, after Newton's death.Although born an Angelican Christian, what sect did he start following in his 30s?Arianism
Saw this on the physicsforums.com twitter feed, so I'm assuming bumping it is okay.
Got satisfactory. For the record I guessed correctly on the publication date , but I got it confirmed by the Roman Numeral question. I don't even know what some of them mean, but I know what LXXXVII means, which is all you need.