His loneliness, paradoxically, has earned him plenty of company. With and without erstwhile partner Art Garfunkel, he has sold millions of albums, and some of his songs—“Bridge over Troubled Water,” to name one—are now pop standards, known to one and all. That’s no surprise, for Simon has always considered his competition to be other standard-setters—Dylan, Lennon, and McCartney—and has aimed to equal or outdo them with every new song.