For instance, there was a time when he teached a course starting with a big number of students. But the students dwindled down as the days went by gettting to a point where there was no longer any student at all!

Still, he went on conducting his lectures even without a single audience as that's how seriously dedicated Newton was with his work. He believed in the goodness of his works.

Indeed, it didn't bother him to lecture to a "ghost audience," he kept on just as to how some of the publishers of this website does including me! He ultimately believed that there's something good coming out of his works.

Well, mankind gravely benefitted with "Newtonian Mechanics & Newton's 3 Laws" - the very core of "classical physics" which is so useful up to this very day!