Whatever is fiery doesn't just rise up because of fire's nature. It's also eager to join with other fire and burn together. Anything that lacks moisture to resist gets set on fire easily. So whatever shares in our common rational nature naturally longs even more for its own kind. The more excellent something is by nature, the more it wants to unite with what shares that nature. Even unreasonable animals quickly form swarms, flocks, and families. They show a kind of mutual love.
Whatsoever is fiery, doth not only by reason of the elementary fire tend upwards; but here also is so ready to join, and to burn together, that whatsoever doth want sufficient moisture to make resistance, is easily set on fire. Whatsoever therefore is partaker of that reasonable common nature, naturally doth as much and more long after his own kind. For by how much in its own nature it excels all other things, by so much more is it desirous to be joined and united unto that, which is of its own nature. As for unreasonable creatures then, they had not long been, but presently begun among them swarms, and flocks, and broods of young ones, and a kind of mutual love and affection.