Book 2 of the Physics is arguably the best introduction to Aristotle's work, both because it explains some of his central concepts, such as nature and the four causes, and because it asks some gripping questions that are still debated today: Is chance something real? If so, what? Can nature be explained by chance, necessity and natural selection, or is it purposive?Philoponus' commentary is not only a valuable guide, but also a work of Neoplatonism with its own views on causation, the Providence of Nature, the problem of evil and the immortality of the soul.