The inquiry into the faculties and functions of living beings is here continued, for the purpose of determining, through them, the source from which life is derived; and the distinction between the animal and vegetable kingdom is, incidentally, alluded to. That distinction is placed in the presence or absence of sentient properties; and so Lamarck distinguishes plants, by their want of irritability, that is sensibility, from animals.
Chapter III.
All the faculties of Vital Principle which have been enumerated belong, as we have said, to some creatures, some only of them belong to others, and there are creatures again which have but one; and we spoke of those faculties as the nutritive, appetitive, sentient, locomotive and cogitative. Of these, the nutritive alone belongs to plants; but to other beings both it and the sentient have been imparted; and if the sentient, then the appetitive, for appetite is desire, passion and volition; and all animals, without exception, have the sense of Touch. But the creature to which sensibility has been imparted cannot but be sensible of pleasure and pain, of what is grateful and what painful; and if sensible of these, it must have desire, as desire is the appetite for what is grateful. All such creatures, moreover, have the sense for food, as they have Touch, which is that sense; for all animals are nourished by what is dry and moist, warm and cold, and Touch is the sense for judging of these qualities. But it is only by chance that the Touch can judge of other qualities, as neither sound, colour nor odour contribute in aught to nourishment; and savour is among tangible qualities. Hunger and thirst are desires: the former for what is dry and warm, the latter for what is liquid and cold; and savour is the condiment, as it were, for both. As, however, we shall be more explicit upon those points hereafter, it may, for the present, suffice to say, that all such creatures as have the sense of Touch have appetite; it is uncertain whether or not they have imagination, but this also shall be considered hereafter. There are creatures to which, besides those faculties, locomotion has been imparted; and others again, as man, to which have been allotted both reflexion and mind, together with any other and yet nobler faculty, if such there be, than mind.
It is clear, then, that there can be but one definition for Vital Principle, as there is but one for a geometrical figure; for as in geometry there is no figure but the triangle and its sequences, so neither are there any kinds of Vital Principle save those which have been enumerated. Could there, however, be any such common expression for figures, as without being peculiar to any one, should yet be applicable to all, so might there be for the Vital Principles alluded to. It would be idle, however, to seek for any such expression, in the case either of Vital Principles or geometrical figures, as should neither be applicable to any one of them individually, nor, putting aside individuals, be applicable to them as an individual species. But still there is an analogy between the faculties of Vital Principle and geometrical figures; for as in vital properties, so in geometrical figures, the antecedent is ever present potentially in the sequences, and as the triangle is in the square, so the nutritive is in the sentient faculty. Thus, the inquiry must be conducted with reference to individuals, in order to learn what is the Vital Principle of each, as of a plant, a man, or a brute; and wherefore beings are thus ranged in a series.
Without the nutritive function there can be no sensibility, but in plants the nutritive exists without the sentient; so again without the Touch there can be no other sense, while Touch can exist alone, for many animals have neither sight nor hearing, and are altogether without smell. Among sentient creatures some have and some have not locomotion, and, finally, to a few calculation and judgment have been imparted; and to such among mortal beings as are so endowed all other faculties have been imparted likewise. But to such as possess some one only of the faculties, calculation has not been allotted, as some of them have not even imagination, while others live by it alone; it would be foreign to our present inquiry to enter upon the speculative intellect.
It is, then, clear that the definition which comes closest to each one of those faculties is also the fittest for the elucidation of Vital Principle.
Notes Layout 2 Note 1, p. 71. And all animals, without exception, have the sense of Touch, &c.] Aristotle, having observed that plants have only the function of nutrition, that is, are not sentient, proceeds to the first and, therefore, most universal of the senses—that which may, as he assumed, be present without any other, although there can be no other without it. Thus, the Touch, as perceptive of food, was supposed to be subservient to the appetite, and the Taste, as discriminating, by tangible qualities, what in food may be genial or otherwise, was held to be a modification of the Touch; but the Touch alone was by Aristotle regarded as distinctive of animal in contrast with vegetable existence. "According to the argument, he adds, by which appetite is said to be the mediate cause of motion, there must, in living animal bodies, be some such medium; and the being, therefore, which by its nature is incapable of motion, is impressionable by appetite, through some other faculty." Plants, that is, are not affected by the appetitive stimulus as are animals.
Note 2, p. 72. As, however, we shall be more explicit, &c.] The Touch being the earliest, so to say, of the senses and distinctive of animal existence, is here held to be the cause of appetite, as appetite is of motion; and as has been observed, the Touch was supposed to exist independently of the other senses. This sense is said to be especially discriminative of food, as animals are nourished by substances which are hot and cold, dry and moist, and these qualities are subject to it; but it can distinguish only by chance such other properties (odour, colour, sound, for instance) as do not contribute to nutrition. It is not easy to attach a definite notion to the imagination here alluded to, but as Aristotle has elsewhere distinguished the rational from the sentient imagination, and as instinct only can be assigned to creatures with one sense, it may be assumed that this is its meaning.
Note 3, p. 72. It is clear, then, that there can be but one, &c.] The triangle forms all rectilineal figures, which have more than three sides, that is, "all such figures may be divided into triangles, as the square into two, the pentagon into three, the hexagon into four, &c.; and geometry has, since that age, reduced this to a special theorem."
Note 4, p. 73. Thus, the inquiry must, &c.] The conclusion here arrived at enforces the necessity of attention to individual existences, in order to ascertain what may be the distinction, if such there be, between Vital Principles; so that the question reverts to former speculations, whether or not there is but one Principle variously imparted, or whether rather, each genus of being has its own special cause of vitality and motion. It belongs, also, perhaps, to the same speculation, to ascertain why beings have been ranged in a series—why, that is, such manifold gradations of existence from man down to the zoophyte; unless, indeed, with other conditions of similar character, it is beyond the pale of human inquiry.
Note 5, p. 73. But to such as possess some one only of the faculties, &c.] It is far from easy to fix upon the exact equivalents of the original terms (λογισμὸς, διάνοια, φαντασία,) which have been here rendered by calculation, judgment and imagination; but the speculative intellect, (θεορητικὸς νοῦς) implies it may "be assumed" the human mind or understanding, which was said to be impassive, homogeneous, and distinct from all else. It might well, therefore, be regarded as foreign to an inquiry, the purport of which is to detect the animating principle of bodies fitted for receiving its influences. It is somewhat strange that Aristotle, whose teaching was so didactic, should nowhere have given a definition of that principle or being, to which he has assigned so exalted a destiny.
PRELUDE TO CHAPTER IV.
The opening paragraphs of this chapter are both obscure and apparently contradictory; for while it is suggested that it might be well, in order to comprehend faculties or functions, first to study the energies or organs from which they emanate, yet the inquiry reverts to nutrition as a fact; without reference, that is, either to vital processes or to food. We may assume that Aristotle was unacquainted with the rudimentary forms and development of the corporeal organs, and yet, judging from this exordium, he seems to have perceived that every part must advance from a nascent state to its perfected condition; and thus he has suggested the teaching of developmental anatomy. As the inquiry proceeds, we are reminded of the obscurity or inaccuracy of language, in portraying the impressions upon and the functions, so to say, of the sentient organs even now the external object is, with us, in common parlance, a sensible object; sensation, besides its own sense, implies casual feelings from within; sight signifies both faculty and function; and nourishment is food as well as digestion. It is somewhat, perhaps, objectionable that Aristotle should have bound up, so to say, the generative with the nutritive function, seeing how they differ both in the periods of development and duration; they are equally necessary, no doubt, to nature's design, but still they are neither contemporaneous nor identical. With respect to spontaneous generation here alluded to Aristotle admitted its possibility, and for obvious reasons, in the case of eels; and, although he denied that all mullets (τοὺς κεστρεῖς φύεσθαι πάντας) are so reproduced, yet he believed that some of the species spring forth (φύεται) from the mud and sand on the sea-shore; and thus it is evident, he continues, that some creatures, not being derived from others, may be the product of spontaneous generation. This opinion upon reproduction prevailed for many ages, and even yet, perhaps, notwithstanding the advancement of science, it may not be altogether discredited.
Chapter IV.
It is necessary, in order well to study those faculties, that we should comprehend what each of them individually is, and then, in like manner, carry our inquiry into their consequences and other conditions. But if it behove us to say what each of them is, as what is the cogitative, sentient, or appetitive faculty, it should previously be settled what that is which thinks and that which feels; for energies and acts are, abstractedly considered, pre-existent to their functions. Granting, however, that it is so, and that we ought, before the faculties or functions, to have considered their opposites, it might be fitting here also, and for the same reason, first to define the opposites of the functions define, that is, food before nutrition; the object before perception; and the intelligible before thought.
Thus we must first speak upon nutrition and generation, for the nutritive faculty is innate in other beings besides animals; it is the primal and most universal influence of the Vital Principle, and through it life is manifested in all beings. Its functions are to generate and to employ nourishment; for the most natural of the functions in beings which are perfect, that is, which are neither dwarfed nor spontaneously generated, is to produce another such as itself, an animal an animal, and a plant a plant, in order that they may partake, to the extent which has been allotted to them, of the Everlasting and the Divine. All creatures yearn after this, and, for the sake of it, they do all that they do naturally; but since such beings cannot, in uninterrupted continuity, partake of the Everlasting and the Divine, because no perishable being can abidingly continue as one and the same; yet each can partake thereof in its own allotted portion, be it larger or smaller, and still continue, if not the same, like the same, and one, if not in number, as species.
The Vital Principle is the cause and the origin of a living body. Now, cause and origin have several significations; for the Vital Principle is equally a cause, according to any one of the three defined modes of causation: as that whence motion proceeds; as that for which motion is produced; and cause, again, as the essence of living bodies. It is evident that it is a cause as an essence, since the essence is in all things the cause of their being what they are; and as life is the mode of being in living beings, so Vital Principle is the cause and the origin of all such. It is the realizing principle, besides, the cause that is of something which exists in potentiality becoming a reality. It is manifest, too, that Vital Principle is a cause, in the sense of a final cause; for as the mind acts for some end, so does nature, and that end is her aim; and such an aim has the Vital Principle, by its nature, in living bodies. Thus, all natural bodies, those of animals as well as those of plants, are its instruments, and are what they are for its purposes. The term final cause has a twofold signification, as it implies that for which, as well as that by which, any result is obtained; and Vital Principle is a, final cause, as that whence locomotion is derived, although this is a property which does not belong to all living creatures. Change and growth, moreover, are dependent upon Vital Principle; for sensation seems to be a change of some kind, and whatever is sentient has Vital Principle; and this applies equally to growth and decay, for nothing grows or decays naturally unless it be nourished, and nothing is nourished which does not partake of life. Empedocles has not expressed himself happily upon this point, as, after other observations, he adds that plants take growth downwards, where they strike root, from this being the natural direction of earth, and upwards, from this being the natural direction of fire. Neither has he clearly seized the import of the terms upwards and downwards, as they are not identical for all creatures, or for the universe; for the nead is to animals what the roots are to plants, if we may speak of organs after their functions, although in other respects different. But, besides these objections, what is that which is to hold fire and earth, with their opposing tendencies, together? Now, unless there be a restraining force, they must be torn asunder, and if such there be, it ought to be regarded as Vital Principle, and the cause both of nourishment and growth.
The nature of fire seems, to some philosophers, to be the absolute cause of nutrition as well as growth, and that because it alone, among bodies or elements, appears to be nourished and to grow. It might, therefore, be assumed, that it is fire which works out those processes in plants and animals; but although fire is possibly a joint cause, it cannot be the exclusive cause, as this must be assigned rather to the Vital Principle. The increase of fire is infinite, so long as there is any thing combustible, but to all the bodies of nature's constitution there is a limit and a relation both as to bulk and increase; and these are conditions, not of fire but of Vital Principle; not of matter but of design.
Since the same faculty of Vital Principle is at once nutritive and generative, it is necessary first to define nutrition; for it is by this, compared with other faculties, that Vital Principle is especially distin- guished. Nutrition, then, appears to be a contrary acted upon by a contrary, but this does not imply any kind of contrary by any other contrary; it refers only to such contraries as can generate from and give growth to one another. Thus, there are many things derived from one another which are not always quantities, as the healthy, for instance, is derived from the unhealthy; neither do these contraries appear, in any manner, to be nourishment for one another, as water, for instance, is nourishment for fire, but fire is not nourishment for water. It is in homogeneous bodies especially, that the contraries seem to be in the relations of nourishment and nourished. But here there is a difficulty; for while some maintain that like is nourished as it is increased by like, there are others who maintain, as we have said, that it is contrary which is nourished by contrary; that like is unimpressionable by like; that food undergoes change and is digested, and that all-change implies conversion to an opposite or an intermediate state. Nourishment, besides, is affected by the body which is nourished, although the body is not affected by the nourishment, just as the material is affected by the artisan, although he is not affected by the material; for it is the artisan alone who converts the material from a raw state into one of usefulness. There is, however, a distinction to be observed in nourishment, between its last and adventitious or its first state; if both states are nourishment, distinguished only by the one being undigested, and the other digested, then it may be correct to admit of both explanations for nutrition; for in so far as food is undigested, it is contrary nourished by contrary, and in so far as it is digested, it is like nourished by like. Thus, it is manifest that both these opinions are in one sense right, and in another wrong. But as nothing can be nourished which does not partake of life, so a living body may be regarded as a body which is nourished from having life; and thus nutrition is not in a casual, but a positive relation to a living body. There is an obvious distinction between nourishment and growth: in so far as a living body is quantity, it is capable of growth, and in so far as a something is matter and essence, it is nourishment; for it preserves the essence of the body, which exists so long as it can be nourished. Nourishment, however, does not generate that which is nourished, as it is the same as it; for it is already itself the essence, and nothing can generate, although it may preserve itself. Thus, it is the same faculty of Vital Principle which is able to preserve that, such as it may be, which contains it, and it is nourishment which renders it fit for its office; and, therefore, when deprived of nourishment, it can exist no longer.
Now, there are here three things or conditions—something to be nourished, something by which nourished, and something which nourishes. That which nourishes is the primal or nutritive faculty; that which is nourished is the body; and that by which nourished is food. And as things are correctly designated after the object to which they tend, and as the object here is to generate another like itself, so the primal faculty may be set down as being generative of another like itself. That “by which nourished” has a twofold signification, as has that by which a vessel is steered, and which implies hand and rudder, of which the one only moves, while the latter both moves and is moved. It is necessary to nutrition that food should admit of being digested, and as it is heat which works out digestion, so all living creatures have heat.
It has thus then be shewn, although but superficially, what nutrition is; but the subject shall be further elucidated in other treatises upon the subject.
Notes Layout 2 Note 1, p. 77. But since such beings cannot, &c.] The purport of this passage is almost too obvious for comment, embodying the great fact of the perpetuation of the species, and compensation, by reproduction, for the death of the individuals; and number refers, of course, to individuals, species to the aggregate.
Note 2, p. 78. The term final cause, &c.] This is a kind of parenthetical clause, intended merely to guard against the supposition that the fact of some animals having a fixed habitat, not being locomotive that is, was unknown, or had escaped notice.
Note 3, p. 78. And this applies equally to growth and decay.] Aristotle perceived, although it may be indistinctly, that the source of nutrition is through the blood—he perceived, that is, that "the blood is replenished by vessels, which arise on and are spread over the mesentery, and which empty themselves into the cava and the aorta;" the anatomy is, no doubt, imperfect, but it still is an outline of the knowledge of the lacteals. It seems to shew that veins gather fluid from the intestines, and convey it to the large blood vessels; but there was no analogous knowledge, in that age, whereby the process of decay that is absorption could be accounted for. The term decay, therefore, was the mere expression for a general fact.
The objection to the terms "upwards and downwards," used by Empedocles to delineate the growth of plants, suggests the advantage that would accrue to science, if its terms were made sufficiently precise to fix, beyond doubt, the several relations and positions of the same body, or all bodies. And in the analogy between the heads of animals and roots of trees, we cannot but perceive the outline of a doctrine which has been developed, by modern science, into homologous physiology.
Note 4, p. 79. The nature of fire seems to some philosophers, &c.] This is an argument, drawn from the agency of fire, to disprove the then prevailing opinion, that, as it alone of the elements appears to be nourished and to grow, it may be the source of life and the origin of living actions; as they are shewn, by the contrast between living and igneous properties, to be essentially distinct from one another. The opinion may have originated from the fact that heat accompanies digestion, and as fire was by some held to be the first element, it was readily supposed to be the agent in that process. As an illustration of this opinion, it was maintained, even by Aristotle, that "food, taken into its appointed receptacles, is vaporised and transmitted to the veins, in which, undergoing change, it is converted into blood, and carried onward to the heart."
Note 5, p. 81. There are here three things, &c.] The meaning of this passage, apart from its scientific wording, is sufficiently obvious—that which nourishes is food when digested; for food both acts and is acted upon by the body, and, when so acted upon, it is assimilated to and incorporated with its substance, through the blood. But food, being dead, is contrary to the living matter, which has, however, power to convert it into like, to assimilate it, that is, to the living system. Thus, food, in its first state, is contrary to or unlike, and in its last, or concocted state, it is like the body; and, therefore, the same element is in one sense contrary, and in another sense like, acting upon a contrary or like. So too the rudder, which directs the vessel, represents the stomach, which converts the food into nourishment for the body; and the sensibility, which gives power to the stomach, represents the hand which, through the rudder, directs the motion of the vessel; and the vessel is analogous to the body which is nourished.
Prelude to Chapter V.
Aristotle, having fully inquired into the process of nutrition, here enters upon the investigation of the sensibility or sentient system, which is, as he said, the line of separation between animal and vegetable existence; the inquiry includes, of course, the senses and their organs, as well as allusions to those external forces or qualities which by their action produce simultaneous perception, that is, sensation. Sensibility is one of the great mysteries of our mortal nature, but its investigation was, in that age, additionally complicated and abstruse, as the brain as well as its relation to the spinal cord and connexion with the organs of the senses were unknown. But, although anatomy has detected the links between the brain and sentient organs, and thus shewn that the senses are emanations, so to say, from it, yet this knowledge, however otherwise valuable, does not explain how matter has been constituted thus to produce sensation, and, by reflexion, consciousness.
Chapter V.
Let us now proceed, as those subjects have been scrutinized, to speak upon sensation in its widest acceptation.
Sensation is the combined result, as has been said, of a motion and an impression, for it seems to be some kind of change; and some writers maintain that it is only like which is impressionable by like, but we have already, in our treatises “upon action and impression,” shewn how far the opinion is or is not tenable. But it is difficult to understand why there is no sensation from the senses of themselves, that is, why, without the presence of external objects, the senses do not give out sensation, although fire, earth, and the other elements, from which or the accidents of which sensation is derived, are present in them. It is evident that it is because the sensibility is not in a state of activity, but is only in potentiality; and, therefore, that it is with it as with a combustible material, which alone, without something on fire, does not burn; for otherwise it might set fire to itself, and would stand in no need of fire, in reality, for the purpose. Since we speak of sentient perception in a two-fold sense, (for we speak of one who hears and sees, in potentiality, as “one hearing and seeing,” although he may happen to be asleep, and we say the same of one who is actually employing those senses,) so may sensation be spoken of in two ways, as subsisting in potentiality and subsisting in activity. Let us, however, before proceeding further, observe that impression, motion, and action are for us equivalent terms—for motion is a kind of action, although an action which is incomplete, as has been elsewhere explained. Now, all things which are impressed and set in motion are so affected by something capable of making impression and existing in activity; so that impression is in one sense by like, and in another sense by unlike, as we have said—for the unlike is subject to impression, but, having been impressed, it is converted into like. A distinction, however, must be drawn between the terms potentiality and reality, for we are now going to employ them in an absolute sense—any individual whatever, then, may be learned, as we might speak of any man as learned, because man is among beings capable of learning and being learned; and so we speak of a man as learned, from his actually professing, at the time, grammatical or other knowledge.
Thus, each of these individuals is learned in potentiality, although in a different manner—the one is so because he is of a certain genus and peculiar matter; and the other, because he can when he will reflect upon his knowledge, provided there is no external impediment to his doing so. It is this one only, however, when actually reflecting upon his knowledge, being in activity, and fully acquainted with some one subject, as A. for instance, who is to be accounted learned in reality. Both those first men, in fact, are learned in potentiality; but the one is so from having been modified by learning, and undergone frequent changes from one habit to an opposite one; and the other is so from possessing sensibility or rudimentary learning, and being able, although in a different manner, to pass from inertia to activity.
But the term impression is not absolute in signification, as sometimes it implies a kind of destruction by a contrary, and sometimes it signifies rather preservation of something being in potentiality by something which is in reality and like, in the relation that potentiality bears to reality. Thus, the possession of knowledge implies the power of reflecting upon it, and this either is not change, being but an increase of knowledge and a step towards its completion, or it is change of a different kind. It is not correct, therefore, to say that an individual, when thinking, is undergoing change, any more than that a builder, when employed in building, is undergoing change; so that the process by which an individual passes, as to his thinking and reflecting faculties, from potentiality to reality, ought to have some other appellation than that of instruction. We may not then, as has been observed, say of the individual who, from being in potentiality, learns and receives knowledge from one who is in reality and able to teach, that he suffers impression, or else it must be admitted that there are two modes of change, one in privative dispositions, and another over habits and nature. The first change, however, of this kind in the sentient being comes from the parent at the moment of conception; as from that moment the being has, as it were, learning and sensibility. There is an analogy between the state of activity and reflexion just alluded to, but with this difference, that the impressions productive of activity, as the audible, the visible, and others, are all derived from without; and the cause of this is that sensation, in activity, is employed upon particulars, knowledge upon universals; and universals are, in some way, in the Vital Principle itself. The act of thinking, therefore, is dependant only upon the will of the individual, which is not the case with sentient perception, as for it there must of necessity be objects to be perceived; and this holds good, and for the same reason, with respect to the sciences which are engaged upon external objects, because all such objects are among particulars, and are external to the percipient. But an opportunity may hereafter present itself for the further elucidation of the subject. Let it, for the present, suffice to say, that the expression being in potentiality has not an absolute signification, for it may be understood of a boy as being qualified potentially to be a General, and also of an individual of suitable age for the office; and the term sensibility is subject to like modifications of meaning. But as the distinction between these two states of sensibility is without any special appellation, although it has been shewn that there is a distinction between them and what the distinction is, it has been found necessary to employ the terms impression and change, as if their signification were unequivocal; but, as has been said, the sentient principle is, when in potentiality, analogous to the external object when in reality.