The Operations of Sentient Bodies

a) Vegetal Operations — b) Sensation — c) Appetition — d) Locomotion — e) Sentient Powers

a) Vegetal Operations

We have already learned that life in bodies is manifested in essentially distinct grades. Therefore, life of the second grade will possess all the perfection of life of the first grade, and will add thereto its own proper and essentially different perfection.

Animals or sentient bodies are living bodies of the second grade. Hence animals possess all the perfection of living bodies of the first or lowest grade (i.e., plants) and, in addition, possess their own proper perfections which are essentially different from (and superior to) those of plants.

It is manifest that animals have the vegetal operations; hence they have the vegetal powers or faculties which are the proximate principles of those operations. Animals take nourishment; they grow to the mature state of their type; they tend to reproduce their kind. Nutrition, growth, and generation are as manifest in animals as in plants. But the essential specific distinction of animals as compared with plants, lies in the fact that animals possess, in addition to vegetal operations and powers, the sentient operations and powers which we are to consider in the following paragraphs.

b) Sensation

The term sensation, frequently used in casual speech to indicate an unusual or startling occurrence, means, in the present instance, a vital operation. It means the activity of sensing which is found, in greater or lesser degree of complexity and perfection, in every animal organism.

To sense an object is to react consciously to an impression received from that object through bodily organs or sensories. Sensation is the conscious reaction, by or through bodily parts, to bodily impression. Sensation is a knowing activity; it is an awareness. It is the awareness in an animal organism of bodily reality manifested by the qualities (common and proper) of such reality,—qualities such as color, sound, shape, hardness, desirability, harmfulness.

When we say that animals have the operation called sensation, we mean that animals are equipped with a knowing power suited to their nature and needs, and that they actually exercise such power. The point needs no proof. We have already identified animals as sentient organisms; we have proved that they are truly alive; and life-activities are exercises of the powers of the organism. The question is not whether animals sense, but what sensing means.

c) Appetition

Appetition, like sensation, is a vital, and therefore an immanent, operation. It is an operation by which an animal organism is moved to do or to acquire what the senses apprehend as good to do or desirable to have. It is a tendency consequent upon sense-knowledge or sensation. Technically, we may define appetition (a term which, with appetite and appetency, comes from the Latin ad “toward” and petere “to seek” or “to strive”) as an immanent operation by which an animal is inclined towards that which the senses apprehend as good.

Every being, living and lifeless, tends to what is suitable or good for it. A being, in other words, tends to fulfill the functions of its nature. Thus, the parts of a body tend to cohere; bodies tend to obey physical laws, such as the laws of gravitation and inertia; certain chemical substances tend to form compounds; the plant tends to grow to maturity and fruitfulness; an organ tends to do the thing it is made for, and thus the eye tends to see, the ear to hear, and so on. In all these examples we have instances of what is called natural appetite or natural appetency: it is the natural striving-towards or seeking-after that which is in line with the functions of nature and the maintenance of natural powers. Thus all beings, lifeless and living, non-sentient and sentient, manifest natural appetency or natural appetite. But appetition is an appetency or appetite which follows upon knowledge and is consequent thereupon. Sentient beings, therefore, have appetition which follows upon sensory knowledge. And if there were no appetition in sentient organisms, the bird would see straw and twigs, but she would not build a nest, for there is nothing in the mere seeing of materials to stir her to the task of building. Without appetition, animals would not, and indeed could not, exercise many of their natural functions. But it is a matter of commonest experience that they do fulfill their functions. It follows inevitably that animals possess the power, and exercise the operation, of appetition.

d) Locomotion

The most obvious manifestation of the fact that animals possess sensation and appetition is seen in this: that animals go after what is sensed and appetized. An animal carries out the tendency of appetition, which is evoked by sensation, and so it moves into action. We know that the dog senses food and wants it from the fact that he goes to it and eats it. Appetition follows sensation; movement follows appetition. Movement which has its roots in knowledge is called spontaneous movement. Now, the spontaneous movement of an animal in response to sensation and appetition is called locomotion.

Locomotion (from Latin locus “place,” and motio “movement”) is the vital, or immanent, operation by which an animal moves itself spontaneously from place to place.

Sentient organisms are all endowed with some capacity for locomotion. Even the simplest one-celled animals have the power of moving from one place to another; and when they are deprived of locomotion, their life is virtually at an end. The locomotive power may be very restricted in certain cases; but it is always present. Even the sea-anemone, fixed to its rock, turns and reaches; the oyster opens and closes; these limited movements are enough to constitute it really an organism, that is, were really alive. Locomotion is a mark of sentient life.

e) Sentient Powers

Every operation has its principle, and its proximate principle; it has its active source. The animal organism is the principle of animal operations, but not the proximate principle. The animal possesses a power or faculty or capacity for its operations, and it is by reason of such capacity that the animal is enabled to exercise its operations. And the animal has as many distinct faculties or capacities or powers for operation as it has distinct kinds of operations.

The animal operations are six in number. First, there are the three operations common to all organisms, viz., nutrition, growth, generation. Then there are, in animals, the operations which belong to an animal as a distinct essential kind of organism, i.e., a sentient organism, and these are the three operations we have just now considered, viz., sensation, appetition, locomotion. Six distinct vital operations must come from six distinct vital powers. We therefore assert that the animal is equipped with six vital faculties or powers of operation, and these are: the nutritive power, the augmentative or growing power, the generative or reproducing power, the sentient or sensing power, the appetitive power, and the power of locomotion.

These powers, rooted in the animal, and actual by virtue of the sentient life-principle, are not to be identified with the organism itself or with the life-principle itself. These are powers which the animal has, not powers which the animal is. These powers are the proximate or immediate principles by which the animal exercises its connatural operations, and they are distinct from the organism, and distinct one from another.

Summary of the Article

This brief Article has set before us a schematic study of the sentient or animal operations and powers. We shall elaborate this same matter with much detail when we come, in a later Chapter, to speak of the sentient life of man. Here we have learned the meaning of sensation, appetition, and locomotion. We have defined these operations, and have illustrated their exercise. We have noticed that the respective operations are distinct one from another, and come from distinct capacities, faculties, or powers of the sentient organism.