 Cosmogony is due to the interplay of the four roots and the two forces. Each of the roots has its specific nature. Some—like fire and water—are traditionally seen as antagonistic; others—like fire and air—are seen as compatible. However, Empedocles did not think the specific natures of the roots could cause them to organize themselves into a cosmos. Hence, he introduces Love and Strife. Love works by bringing together roots of different types into harmony. It does so by instilling attraction among the different types of roots for one another; without Love, these roots would not naturally cohere. While it is true that Love then pulls what is similar apart from what is similar, it does not do so by causing repulsion for one another in similar roots. By contrast, Strife aggregates similar roots together by instilling repulsion among different types of roots for one another. The work of Strife is to replace the attraction among different types of roots instilled by Love with repulsion. During the history of a cosmos, these forces are in contention, present together in waxing and waning strengths, throughout the coming to be of the cosmos and its creatures and in their passing away.