Assume that his mass in a deep crouch is concentrated 0.75 mm from the half-pipe. If he remains in that position all the way up, what initial speed does he need to reach the upper edge

John Stuart Mill is arguing against conformity. The human being, through its faculties of "perception, judgment, discriminative feeling, mental activity, and even moral preference", only excercices those faculties when going against custom, against what is known as received wisdom. If someone merely follows the dictates of custom, then he is not thinking, or judging, or making moral choices: he is, so to speak, on autopilot, or simply following the herd. He is not asserting himself as an individual in full command of his humanity. In our daily lives we face many situations where we follow preestablished behaviors: at work, in the street, when dealing with our family. But it is only when we depart from what is expected from us that we become individuals, when we reject the well-worn path of custom and make personal choices.