Elvis did it. Bob Dylan did it. Even Jack Benny did it. But it seems unfair somehow that one particular mortal must cross that most dread of life's mileposts. This week, on July 26, precisely 14,610 days after he was born in Kent, England, Michael Philip Jagger is turning 40. Years ago Mick told the world, "I don't want to be singing Satisfaction when I'm 40." A while later, perhaps already hearing time's winged chariot at his back, Jagger scoffed off the remark as ignorant chaff from "a towheaded lad." Then two years ago, he further temporized: "I mean, it's not very old to be 38. My father was running competitive three miles when he was 38." More recently Mick was almost humble. Said he: "I wouldn't mind singing old Rolling Stones songs when I'm 45." At this rate, we can expect him to be singing Time Is on My Side when he's 65. In the meantime, let us contemplate on the following pages how, even for a rocker of ages, the child (top) is father to the man.