First, whereas it has been assumed above that Xenophanes was theologian rather than philosopher, whence it would seem to follow that the philosophical doctrine of unity originated, not with him, but with Parmenides, Zeller, supposing Xenophanes to have taught, not merely the unity of God, but also the unity of Being, assigns to Parmenides no more than an exacter conception of the doctrine of the unity of Being, the justification of that doctrine, and the denial of the plurality and the mutability of things.
James Hutton (1726-1797) had set forth (1788) the principle that during all geological time there has been no essential change in the character of events, and that uniformity of law is perfectly consistent with mutability in the results.
Buffon, in a cautious, tentative fashion, suggested rather than stated the mutability of species and the influence of the forces of nature in moulding organisms. Immanuel Kant, in his Theory of the Heavens (1755), foreshadowed a theory of the development of unformed matter into the highest types of animals and plants, and suggested that the gradations of structure revealed by comparative anatomy pointed to the existence of blood relationship of all organisms, due to derivation from a common ancestor.
The chief contributions of Cuvier's great philosophical opponent, Etienne Geoffroy St Hilaire (1772-1844), are to be found in his maintenance with Lamarck of the doctrine of the mutability of species.
In a survey of the palaeontological history of plants and animals, it is plain that extreme stability and extreme mutability both have occurred, sometimes having persisted for untold ages, sometimes having succeeded one another for varying periods.
His cosmology was an assertion not so much of the immutability of the One as rather of the mutability of the Many.