Now those who at the very beginning set themselves to this kind of inquiry, and said the substratum was one, were not at all dissatisfied with themselves; but some at least of those who maintain it to be one as though defeated by this search for the second cause say the one and nature as a whole is unchangeable not only in respect of generation and destruction (for this is an ancient belief, and all agreed in it), but also of all other change; and this view is peculiar to them.