'I am a Natural Philosopher, and my Rules are the God-given Rules of the Universe, not the arbitrary ones of your insipid sport!' Roger thundered. 'The ball transfers its vis viva into another ball, the quantity of motion is conserved, all is more or less orderly.' Roger now opened one hand to reveal that he had snatched another ball. 'Or, I may toss it into the air thus – ' he did so " – and it describes a Galilean trajectory, a parabola.' The ball plonked down squarely into a mug of chocolate, halfway across the room; its owner recovered quickly, raising the mug to Roger's health. 'But comets adhere to no laws, they come from God only knows where, at unpredictable times, and streak through the cosmos on their own unfathomable trajectories. So, I ask you, Daniel: Is Newton like a comet? Or, like a billiard ball, is he following some rational trajectory I have not the wit to understand?'