Aristotle was the first who divided quadrupeds into whole-hoofed, cloven-footed, and digitated, and he allows, that the hog is of an ambiguous species; but the only reason he gives is, that in Illyria, Pæonia, and some other places there are hogs with whole hoofs. This animal is also a kind of exception to the two general rules of nature, namely, that the larger the animals the less young they produce, and that digitated animals are the most prolific. The hog, though far above the middling size, produces more than any other quadruped. By this fertility, as well as by the formation of the ovary of the female, it even seems to form the extremity of the viviparous species, and to approach the oviparous. In short, the hog seems to be of an equivocal nature, or rather appears so to those who suppose the hypothetical order of their ideas to be the same as the common order of Nature, and who only perceive, in the infinite chain of beings, some apparent points to which they would refer every natural occurrence. It is not by circumscribing the sphere of Nature that we can become perfectly acquainted with her: we cannot judge of her by making her act with our particular views; nor is it by ascribing our ideas to her Author that we can penetrate into His designs. Instead of confining and limiting the powers of Nature, we should extend them to immensity; we ought to look on nothing as impossible, but that every thing which may be, really has existence. Ambiguous species, and irregular productions, would then cease to surprise, and appear equally as necessary as others in the infinite order of things; they fill up the intervals, form the immediate points, and mark the extremities of the chain. These beings present to the human understanding curious examples, where Nature, appearing to act less conformably to herself, makes a greater display of her powers, and enables us to trace singular characters, which indicate that her designs are more general than our confined views, and that if she does nothing in vain, neither is she regulated by the designs we attribute to her.