We exist, therefore, without knowing how, and we think without knowing why; but whatever is the manner of our being or thinking, whether our sensations are true or false, the result of them are not less certain. This order of ideas, this train of thoughts, which internally exist from ourselves, although very different from the objects that cause them, give rise to the most real affections, and occasion relations with external objects, which we may consider as real affinities, since they are invariable, and always the same. The human species, therefore, may be said to hold the first rank in the order of nature, the brute creation the second, vegetables the third, and minerals the last; for although we cannot clearly distinguish between our animal and spiritual qualities, and although the brute creation are endowed with the same senses, possess the same principles of life and motion, and perform a number of actions like man, yet they have not the relation with external objects in the same extensive manner we have, and consequently the resemblance must fail in various respects. The distance is greater between man and vegetables, and still more so from minerals, as vegetables possess a degree of animation, while minerals are destitute of every principle that tends to organization. To compose, therefore, the history of an animal, we must first nicely inspect into the general order of his particular relations, and afterwards distinguish those he has in common with vegetables and minerals. An animal has nothing in common with a mineral, excepting general properties of matter; his nature and oeconomy are totally different: the mineral is a mere senseless and inactive matter, without organization, faculties, or power of reproduction; a dead mass, fit only to be trod under foot by man and animals; even the most precious metals are thus considered by the philosopher, as they possess but an arbitrary value, subordinate to the will, and dependent on the convention of men. In an animal all the powers of nature are united; the properties by which it is animated are peculiar to it; by its senses it can will, act, determine, and communicate with the most distant objects: its body is a centre, to which every thing is connected; a point where the whole universe is reflected; a world in miniature. These are the properties which peculiarly belong to it; those which it possesses in common with vegetables are the faculties of growth, expansion, reproduction, and increase. The most apparent difference between animals and vegetables seems to be the faculty of moving from place to place, which animals are endowed with and vegetables not. It is true we are not acquainted with any vegetable that has a single progressive motion; and there are many kinds of animals, as oysters, &c. to which this motion seems to have been denied; the distinction, therefore, is neither general nor necessary.