*Note: I said that before I began commentary on Book 2, I’d write an outline of Book 1. Unfortunately that project is taking longer than I expected. I still intend to complete it, but thought in the meantime I would go ahead and begin Book 2 anyways.
Having completed Book One of the Physics, in which Aristotle explored the fundamental principles of nature, we turn now to Book Two, which begins with asking what nature itself is:
“Of things that exist, some exist by nature, some from other causes. ‘By nature’ the animals and their parts exist, and the plants and the simple bodies (earth, fire, air, water)–for we say that these and the like exist ‘by nature’. All the things mentioned present a feature in which they differ from things which are not constituted by nature. Each of them has within itself a principle of motion and of stationariness (in respect of place, or of growth and decrease, or by way of alteration). On the other hand, a bed and a coat and anything else of that sort, qua receiving these designations — i. e. in so far as they are products of art — have no innate impulse to change. But in so far as they happen to be composed of stone or of earth or of a mixture of the two, they do have such an impulse, and just to that extent–which seems to indicate that nature is a source or cause of being moved and of being at rest in that to which it belongs primarily, in virtue of itself and not in virtue of a concomitant attribute” (Physics 2.1, 192b8-23) .
As Aquinas points out, Book One of the Physics was primarily directed towards the “principles of natural things”, whereas Book Two is primarily directed towards the “principles of natural science” itself (Lectio 1.141) . To know the principles of any science, we must first know “its subject and the method by which it demonstrates” . And the subject of natural science is, of course, nature; hence the discussion of the definition of nature. Continue reading