The reason Newton's laws are an improvement over Aristotelian "the nature of water is etc." is that Newton lets you make predictions, while Aristotle does not. You could ask "but WHY does gravity work like so-and-so?", but that doesn't change the fact that Newton's laws let you predict orbits of celestial objects, etc., in advance of seeing them.
That's certainly the conventional wisdom, but I think the conventional wisdom sells Aristotle and his contemporaries a little short. Sure, speaking in terms of water and air and fire and dirt might look a little silly to us now, but that's rather superficial: when you get down to the experiments available at the time, Aristotelian physics ran on properties that genuinely were pretty well correlated, and you could in fact use them to make reasonably accurate predictions about behavior you hadn't seen from the known properties of an object. All kosher from...
Another month has passed and here is a new rationality quotes thread. The usual rules are: