Buffon confirms this last assertion by quoting the sheep as an example--an animal which can now no longer exist in a wild state. Then returning to cattle, he repeats that many varieties have been formed by the effects--"diverse in themselves, and diverse in their combinations--of climate, food, and treatment, whether under domestication or in their wild state." These are the main causes of variation ("causes generales de variete"),[106] among our domesticated animals, but by far the greatest is changed climate in consequence of their accompanying man in his migrations. The effects of the foregoing causes of modification, especially the last of them, are repeatedly insisted on in the course of the forty pages which complete the preliminary account of the buffalo. What holds good for the buffalo does so also for the mouflon or wild sheep. This, Buffon declares to be the source of all our domesticated breeds: of these there are in all some four or five, "all of them being but degenerations from a single stock, produced by man's agency, and propagated for his convenience."[107] At the same time that man has protected them he has hunted out the original race which was "less useful to him,"[108] so that it is now to be found only in a few secluded spots, such as the mountains of Greece, Cyprus, and Sardinia. Buffon does not consider even the differences between sheep and goats to be sufficiently characteristic to warrant their being classed as different species. "I shall never tire," he continues, "of repeating--seeing how important the matter is--that we must not form our opinions concerning nature, nor differentiate (differencier) her species, by a reference to minor special characteristics. And, again, that systems, far from having illustrated the history of animals, have, on the contrary, served rather to obscure it ... leading, as they do, to the creation of arbitrary species which nature knows nothing about; perpetually confounding real and hypothetical existences; giving us false ideas as to the very essence of species; uniting them and separating them without foundation or knowledge, and often without our having seen the animal with which we are dealing."[109] _First and Second Views of Nature._ The twelfth volume begins with a preface, entitled "A First View of Nature," from which I take the following:-- "What cannot Nature effect with such means at her disposal? She can do all except either create matter or destroy it. These two extremes of power the deity has reserved for himself only; creation and destruction are the attributes of his omnipotence. To alter and undo, to develop and to renew--these are powers which he has handed over to the charge of Nature."[110] The thirteenth volume opens with a second view of nature. After describing what a man would have observed if he could have lived during many continuous ages, Buffon goes on to say:--