As we are now entering upon the study of Vital Principle, and are encompassed with doubts which ought to be resolved, it will be incumbent upon us to gather the opinions of such of the earlier writers as have suggested any thing concerning it, in order that we may be able as well to adopt their happier conceptions as to be on our guard against their errors. The suitable opening for this inquiry into the Vital Principle is to lay down the properties which appear, most especially, to belong to it. The animated being, then, seems to be especially distinguished from whatever is inanimate by the two properties of motion and feeling; and these two are almost the only distinctions which have been transmitted to us by the earlier writers upon the subject. Thus, some of them maintain that the Vital Principle is in the largest, fullest sense a motor power; and as they believed that nothing can impart motion unless it be self-motive, they assumed that the Vital Principle must be among beings which are self-moved. Hence Democritus says that it is a kind of fire and heat, and as forms and atoms are, according to him, infinite, he speaks of those which are spherical and apparent in the sun's beams, while passing through chinks in doors, as fire and Vital Principle; and further says, that those atoms, collectively, are the elements of universal nature. Leucippus, in like manner, is disposed to regard the spherical atoms as Vital Principle, both on account of those forms being best adapted for penetrating every where, and best able, from being self-motive, to give motion to other things; and thus they both assume that it is Vital Principle which imparts motion to living beings. Hence, too, they make breathing to be the boundary of life—for they maintain that the envelopment of animal bodies crushes by its contraction those forms of atoms which, from never being at rest, give motion, and that compensation is afforded for their exit by the entrance of other like forms, during inspiration; and that these forms, while entering, resist the contracting and solidifying power, and preclude the expulsion of all the atoms which are essential to life. They further maintain that animals can live only so long as they can support this process. The opinion adopted by the Pythagoreans seems to be to the same purport—for some of them have maintained that Vital Principle is the motes in the air, and others that it is that which gives motion to the motes; and it has thus been said of those corpuscles, because of their appearing to be constantly moving, although the air may be quite still.
To the same point do they also come who say that the Vital Principle is self-motive ; for all these philosophers seem to have assumed that motion is the most characteristic property of the Vital Principle ; and that, while all other things are moved by it, it is self-moved, and the more so, as they do not see any motor which is not self-moved.
Anaxagoras, in like manner, says that the Vital Principle is a motive force, and the same opinion may be attributed to any one who, with him, may have maintained that the mind has given motion to the universe; and yet his opinion is not altogether in accordance with that of Democritus. Democritus, in fact, maintains that Vital Principle and mind are absolutely identical ; that the apparent is the true; and that Homer, therefore, has done well in representing Hector as "changing his mind while he lay." Thus he does not employ the term mind as a faculty for the attainment of truth, but makes mind to be identical with the Vital Principle. Anaxagoras is less explicit upon these points ; for, in many places, he speaks of mind as the source of the beautiful and the true, while, elsewhere, he says that it is identical with the Vital Principle, and innate in all creatures, larger or smaller, higher or lower, in the scale of being ; but it is manifest that mind, in the sense of intellect, is not equally allotted to all animals, nor even to all men.
Thus they who have looked upon living beings with respect to motion, have assumed that the Vital Principle is the most motive of entities, and so many as have looked upon them with respect to knowledge and sentient perception, have said that the Vital Principle comprises all first causes; of which, while some admit of several, others maintain that there is only this one. Empedocles, for instance, seems to maintain that the Vital Principle is derived from all the elements, and that each element is Vital Principle, as he says that " by earth we perceive earth, by water water, by air air, by fire destructive fire, by attraction attraction, and by repulsion dire repulsion."
Plato, in a like manner, in the Timaeus, derives the Vital Principle from the elements—for like, therein, is known by like, and things are derived from first causes; and so, likewise, have things been denned by him in the treatises "upon philosophy." According to them, animal, in itself, is derived from the abstract idea of unity, and primal length, and breadth, and depth; and other things in a somewhat similar manner. It is besides maintained, but in a different sense, that the mind is unity, and knowledge duality, although, as one branch, it is unity; and that the number of the surface is opinion, that of the solid sensation, for numbers were spoken of by him as forms and first causes, and as derivatives from the elements. Thus, some things are discriminated by mind, some by knowledge, some by opinion, and others by sensation; as the numbers which represent those faculties are the forms of things.
Since the Vital Principle has to some appeared to be both motive and capable of knowing, there are writers who have combined motion and intelligence, and then represented the Vital Principle as a number endowed with self-motion.
Philosophers differ with respect to first causes, both as to their nature and number; but they who make them corporeal differ most from those who hold them to be incorporeal; and from these again they differ who make them to be a combination both of corporeal and incorporeal molecules. They differ also with respect to the number of such causes, as some adopt only one while others admit of several; and, in accordance with these conclusions, they form their estimate of the Vital Principle ; but yet they have all assumed, and not unreasonably, that it is of the nature of first causes to be motive. Hence, the Vital Principle has to some appeared to be fire, as fire, besides being the most attenuated and most incorporeal of the elements, is both self-motive and a primal cause of motion in other things.
Democritus has expressed himself more clearly than any other writer in specifying the causes of each of those properties: for he says that the Vital Principle is identical with the mind, and to be placed among primal and indivisible bodies; that it is motive, owing to the tenuity of its parts and its form; that of forms the spherical is the most mobile, and that this is the form both of mind and fire.
Anaxagoras seems, as we have already said, to distinguish the mind from the Vital Principle, although he employs both terms as if synonymous; excepting that he sets down the mind as being, in the fullest sense, the origin of all things. Thus he says that the mind alone of all entities is homogeneous, unmixed, and pure; and to the same principle he attributes the properties both of knowing and imparting motion, as he maintains that it is the mind which has given motion to the universe.
Thales, too, from what has been recorded of him, seems to have assumed that the Vital Principle is something motive, since he said that the loadstone must have a Vital Principle because it gives motion to iron.
Diogenes, together with some other writers, held the Vital Principle to be air, because air was believed to be the most attenuated of the elements, as well as an originating cause; and that, through these properties, the vital principle is able both to recognise things and to impart motion to them. They argued that Vital Principle, as being a first cause and the origin of other things, is able to recognise them; and that, as being the most attenuated of entities, it is motive.
Heraclitus also maintains that the Vital Principle is a first cause, since, in his system, it is the exhalation out of which he constitutes every thing else ; he regards it too as the most incorporeal of entities, and as being "in a constant state of flux;" and further says, that the moved must be known to the motor. He agreed, in fact, with most others in believing all things to be in motion.
The opinions of Alcmaeon upon the Vital Principle seem to be very like those just cited—for he says that it is immortal, on account of its resemblance to the immortals, and that this resemblance is manifested by its being continuously in motion; for all divine bodies, he argues, the moon, sun, stars, and heavens, are continuously moving.
Some writers of smaller pretension—and Hippo was one of them—have ventured to represent the Vital Principle as water; and they seem to have been led to this persuasion by the nature of semen, which, in all creatures, is fluid. Hippo, indeed, reproves those who assert that the Vital Principle is blood, because blood is not semen; and semen is, according to him, the first principle of life.
Others have maintained, as did Critias, that the Vital Principle is blood, from their assuming that the most peculiar property of blood is feeling, and that feeling is imparted to us through the nature of blood. All the elements, in fact, have had their partisans, excepting earth; and no one has adopted it, unless such an opinion may be attributed to those who have derived the Vital Principle from all, or made it to be all the elements.
Thus, all these philosophers define Vital Principle by the three properties, motion, feeling, and incorporeity, each of which is referrible to first causes. Such of them, therefore, as define it by the faculty of knowing, make it to be an element or a derivative from the elements, and, with one exception, their opinions coincide;—for they all maintain that like is known to like, and, since the Vital Principle recognises all things, they constitute it out of all first causes. But such as admit of only one cause and one element, set down Vital Principle as being that one, be it fire or air ; and such as admit of several first causes, set down Vital Principle as being multiple also. Anaxagoras stands alone in maintaining that mind is impassive and without anything in common with aught else ; but, even were it so, he has not explained, nor is it easy from what he has said to explain, how or for what purpose it is to recognise anything. So many writers as admit contraries among first causes, constitute the Vital Principle out of contraries, and so many as admit only one contrary, whether hot or cold, or other analogous contrast, make the Vital Principle to be that one. Hence, led by the terms, some maintain that Vital Principle is heat, because from heat the term life has been adopted; and others affirm that it is cold, because from cold, through respiration, the term Vital Principle has been derived.
Such, then, the opinions which have been transmitted to us upon Vital Principle, and such the reasons upon which those opinions have been grounded.