As for mutual helpfulness, those very things1 which we have called inanimate are for the most part themselves produced by man's labours; we should not have them without the application of manual labour and skill nor could we enjoy them without the intervention of man. And so with many other things: for without man's industry there could have been no provisions for health, no navigation, no agriculture, no ingathering or storing of the [p. 181] fruits of the field or other kinds of produce.