Since that which is evident and, when abstractedly considered, more apprehensible may be derived from particulars which are by their nature obscure, although to us more apparent, let us again attempt, bearing this in mind, to attain to a comprehensive view of Vital Principle. It is not only correct that the wording of a definition should shew, as do most definitions, what a thing is, but it ought also to embody and make apparent the cause of its being what it is. But the terms usually employed make definitions to be kinds of conclusions; as if, for instance, to the question "what is a quadrature?" it be answered, that it is to find an equilateral rectangular figure equal to another figure with unequal sides, such a definition is the statement of the conclusion; if it be said that the quadrature is "the discovery of a mean proportional," this conveys the cause of the thing.
We say, then, resuming our inquiry at its outset, that the animate is distinguished from the inanimate by having life. Now the term life has many acceptations but if one only of the following properties, viz. mind, sensibility, locomotion, and rest, as well as the motion concerned in nutrition, growth, and decay be manifested in any object, we say that that object is alive. And, therefore, all plants seem to be alive, for they all appear to have within them a faculty and a principle by which they acquire growth and undergo decay in opposite directions; for they do not grow upwards exclusively, but they grow equally in both these and all other directions, and are alive throughout so long as they are able to imbibe nourishment. It is possible for nutrition to subsist independently of the other functions, but the others cannot possibly, in mortal beings, subsist without it; and this is manifest in plants, since no other than it has been allotted to them. Thus, it is by this faculty of nutrition that life is manifested in living beings, but an animal is characterized above all by sensibility; for we say that creatures endowed with sensibility are not merely living beings but animals, although they may neither be motive nor change their locality. Touch is the sense first manifested in all creatures, and, as the nutritive faculty can be manifested independently of Touch and other senses, so the sense of Touch can be manifested independently of any other. We call nutritive function that part of Vital Principle of which plants partake; but all animals appear besides it to have the sense of Touch; and we shall, hereafter, explain why each of those functions has been allotted. Let it suffice, for the present, to say that Vital Principle is the source of the nutritive, the sentient, cogitative and motive faculties; and that by them it has been defined.
It is easy, with respect to some of those faculties, to perceive, whether any one of them is the Vital Principle, or a part of Vital Principle, and if a part whether it is distinct from other parts substantively, or in an abstract sense only; but there are others which seem to elude investigation. Thus, as some plants appear, after having been divided, and after the parts have been separated, still to be alive, as if the living principle, in each plant, were in reality one, in potentiality more than one, so we see the same occurrence in other distinctions of the Vital Principle, as in insects which have been divided; for each of the parts manifests sensibility and locomotion, and if sensibility, then imagination and desire, as wherever there is feeling, there must be sense of pain and pleasure, and wherever these, there must, of necessity, be desire. We have nothing very certain to offer upon the subject of the mind and the reflective faculties; but the mind seems to be another kind of Vital Principle, and alone to be capable of existing apart from the body, as the everlasting exists apart from the perishable. Thus, it is manifest, from what has been adduced, that the other parts of the Vital Principle are not, as some say, distinct from the body, although it is clear that, when considered absolutely, they are different from it; for the mode of being in a sentient must differ from that in a cogitative being, since feeling differs from thinking, and this applies equally to other functions and faculties. All those faculties besides belong to some animals, particular ones only to others, and there are others to which one only has been allotted, and this constitutes distinctions among animals, the cause of which shall hereafter be considered. But something very like this has taken place with respect to the senses, for some animals have them all; others have particular ones only, and there are others again which have but one; but that one is Touch, which of all is the most necessary.
As that by which we live and feel, like that by which we understand, has a twofold signification, since we speak of that by which we understand sometimes as Knowledge, and sometimes as the Vital Principle, for we say that we understand by either of them ; so equally does this apply to that by which we are in health, and which sometimes refers to a particular part of the body, and sometimes to the whole body. Now, the two faculties alluded to, knowledge and health, are a form, a " specific something", a " relation," and an action, as it were, of a recipient, capable in the one case of knowing, and in the other of maintaining health (for the action of creative energies seems to be innate in the impressionable and suitably constituted subject), but the Vital Principle is that by which we live, feel and think, from life's outset; so that, although it may be the cause and form, it cannot be matter and subject. Thus, the essence has a threefold signification, as we have said, in the sense of form, of matter, and the compound of the two; and of these matter is potentiality, and form reality ; and since the living being is a compound of the two, the body is not the reality of the Vital Principle, but it, on the contrary, is the reality of a particular kind of body. On which account it is happily assumed by some that the Vital Principle can neither be without the body, nor be itself a body of any kind; for a body it is not, but yet it is something of the body, and, therefore, present innately in the body, and that peculiarly constituted. It is not, that is, in any kind of body, as the earlier writers have maintained, when they attached it to a body without in the least defining either the nature or quality of the body; although it must be against all probability that any kind of recipient should receive any thing taken by chance. But here all takes place as might reasonably be expected—for the realising influence exists congenitally in its own subject, while yet potential, and constituted of matter fitted for its agency. It is then manifest, from what has been adduced, that the realising influence and cause can act only upon that which is potentially capable of becoming such or such a reality.