lell to decide whether the immediate cause of the change (i.e. the relat the hang-glider or the observer. This suggestion for how to distinguish absolute space, but it is not very clear. Leibniz never ive m otion) is in ish absolute from relative motion avoids all ref g eterence to explain explains what it means for the immediate cause of the change’to a he in an object. But it may be that he intended to reject Newton’s assumption that can only be a fact about the oblect’s relations to something else. an object’s motion, whether relative or absolute. 을 the One of the intriguing things about the absolute /relational controvery is that it refuses to go away. Newton’s account of space was intimately bound up with his physics, and Leibniz’s views were a direct reactionLinned to Newton’s. So one might think that advances in physics since therli 17th century would have resolved the issue. But this has not happened. Although it was once widely held that Einstein’s theory of relativity had decided the issue in favour of Leibniz, this view hasOur fo increasingly come under attack in recent years. More than 300 years task, after the original Newton/Leibniz exchange, the debate continues. straigh sed to What are biological species? Scientists often wish to classify the objects they are studying not ag nter defini defini of con into general kinds or types. Geologists classify rocks as igneous, 96