The opening of Book II of Aristotle’s Physics, the treatise on the principles of changeable things. He begins by marking off what exists “by nature” from what exists “from other causes”, and the distinction fixes the subject of natural philosophy for the tradition that followed.
Read in contextOf 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.