Aristotle’s notion differs from the usual conception of a soul as some sort of substance occupying the body, existing separately and eternally. To him, the soul is the essence of a living thing. The soul is what makes an organism an organism at all by actualizing its potential for life, and it’s constituted by its capacity for activities essential to that specific type of being. His investigation into the nature of the soul demonstrates basic principles of his philosophical theories at work, including Hylomorphism, potentiality and actuality, and his four causes.
His use of these theories in analyzing and teasing out the complexities of the soul make for a cohesive and comprehensive study, easily amenable with his other works. In this paper I will analyze his notion of the soul as described in De Anima, recounting how he came to define the soul, the explanation of the soul, how the souls of different kinds of ensouled beings differ, and his unique concept of how the soul is related to the body.
Aristotle begins Book 1 of De Anima by stating that since the soul is a principle of animals, and here I will interpret animals to mean more broadly beings, describing its essence has implications beyond its obvious scope. In unfolding the nature of the soul, it is possible to determine which attributes belong to the soul alone and which belong to the organism in virtue of having a soul (Aristotle, De Anima 402a). So besides exploring the nature of life, his analysis will also seek to answer the question of whether all mental states (of the soul) are also material states of the body, or whether some attributes of the soul are unique to it.
In doing so, we are confronted with the interesting implication of Aristotle’s position on the mind/body problem, to which I will get to later on. Returning to the question at hand (what is the soul? ), Aristotle starts his investigation by use of his explanatory theory of Hylomorphism, which states that substances are compounds of matter and form, and change occurs when form actualizes matter (Shields). There are three sorts of substances; form, matter, and the compound of form and matter. Matter is potentiality and form is actuality.
Form actualizes matter, which possesses the potential to be what it is. So using Aristotle’s example of a bronze statue, the matter, in this case the bronze, only actualizes it’s potential of being a statue when it acquires the form, or the shape and features. Of interest is the third kind of substance, compounds, which make up living beings. The body is the substance as matter, so the soul is the substance as form or shape. Here we get to Aristotle’s preliminary definition of the soul as the actuality of a natural body having life potentially (Aristotle, De Anima 412).
It is in virtue of this form, the soul, that makes an organism alive. Without the soul, the body would only have the capacity for life potentially, and so the soul is the essence (the form) of living things. This preliminary definition is taken a step further when Aristotle identifies the soul as the “first actuality of a natural body that is potentially alive” (Aristotle, De Anima 412a). He claims that the actuality that is the soul is like the actuality that is knowledge, in that we speak of it in two ways.
We can distinguish between a state of knowing x and a state of attending to the knowledge of x, where the latter is more of an active process. The passive of state of knowing x is the first actuality, first because it must necessarily come prior to attending or remembering that knowledge i. e. potential precedes actual. Similarly, the soul of a sleeping person is like the passive state, the first actuality, while the soul of an awake person is like the active state.
The soul must be the first actuality, for if not we would be forced to say a sleeping animal lacks a soul, a conclusion we do not want to make (Aristotle, De Anima 412a-412b). First actuality seems to correspond to a capacity to engage in the activity of the second actuality, and in this way is a kind of potential to exercise some function, like the ability to engage in thought. Aristotle makes this clear when he states that, “If the eye, for instance, were an animal, sight would be its soul” (Aristotle, De Anima 412b).
Sight is the capacity of the eye for seeing, where sight is the form and the eye is the matter. The first actuality is the capacity for seeing, and the second actuality is seeing, actively exercising the potential ability. So it seems that beyond defining the soul as the ‘first actuality of a natural body that is potentially alive’, we can say the soul is a set of capacities that characterize living things. These characteristic capacities are different in different beings, and we will see that it is by these that Aristotle creates his hierarchy of ensouled beings or the degrees of souls.
I will return to this distinction later in this paper, when describing how the souls of different ensouled beings differ. At this point we have a definition of the soul, but as Aristotle stresses throughout his various works, we must determine the cause or explanation in order to truly grasp the essence, and therefore get at complete picture of his view of the soul. The definition just given explains the what, but a full account must explain the why. He states in the Physics, “for our inquiry aims at knowledge; and we think we know something only when we find the reason why it is so, i. . , when we find its primary cause” (Aristotle, Physics 194b).
His criteria for an adequate definition, one that is sufficient for knowledge, rest on his theory of causation and explanation. The four causes include the material cause, formal cause, efficient cause, and final cause. Material cause is what something is made of, the formal cause is the form or pattern of which a thing is what it is, the efficient cause refers to the agent of change or rest, and the final cause is the intended purpose of the change or the reason why a thing is done (Shields).
We must, therefore, determine why the soul is what it is in virtue of these four general causes. The soul is the principle and the cause of the living body, for it is in virtue of the soul that the body is alive, and thus it plays an explanatory role. It is the cause of the living body in three of the four ways, as “the source of motion, as what something is for, and as the substance of ensouled bodies”(Aristotle, De Anima 415), corresponding to the efficient cause, the final cause, and the formal cause respectively.
It is the source of motion in that it causes growth and decay in the organism. The soul is also the cause of the living body by being the final cause, as the body is merely an organ for the sake of the soul, aimed at the soul. And finally, the soul is the formal cause of the living body for it causes life by being the form and actuality of what is potentially. The body makes up the fourth cause, the material cause, by being the matter that makes up a living organism (Aristotle, De Anima 415).
I will use Aristotle’s example of the nature of a house as described in Book One, when he is discussing the importance of form, in order to better illustrate the necessity for analysis of a concept under his theory of causation and explanation. To merely define a house as stones, bricks, and timbers, is not to capture its full essence. A house is stones, bricks, and timbers (material cause), built into an enclosed structure (formal cause), fashioned together by a carpenter (efficient cause), in order to provide shelter from the elements (final cause).
We can describe the what, but without further details about the explanation, we don’t really know the nature of a house. Similarly the soul is why, it gives the explanation for, the life activities of a living body. At this point Aristotle’s notion of the soul is quite clear; it is the first actuality of a natural body that is potentially alive, it is a set of capacities for life-giving and defining activities of organisms, and it is the form, the source of motion, and the means (it directs) to the end of the living body.
Souls of different living beings are differentiated by their capacities to engage in the activities characteristic of that type of organism, which comprise their livelihood and survival. It is these differentiating faculties that make up the soul. Among these faculties are the nutritive and reproductive, perceptive, locomotive, and the capacity for thought and understanding. Aristotle claims, “the soul is the principle of the potentialities we have mentioned—for nutrition, perception, understanding, and motion—and is defined by them” (Aristotle, De Anima 413).
There are three types of souls, arranged in a nested hierarchy, so the possession of a higher soul entails possession of all that are below it. The lowest, or most basic, in this hierarchy is the nutritive soul. All living things possess the capacity for self-nourishment, for without this they would not live. Next is the sensitive soul, which is possessed only by animals. The highest type of soul is the rational soul, belonging only to humans. These three souls are differentiated by their function, corresponding to the ensouled being in possession of the soul with the power to exercise that function.
While the animal soul possesses the nutritive and the sensitive, and the human soul the rational as well, each has but one unified soul with a various sets of capacities (Shields). The nutritive soul is the potentiality held by all living things to preserve it and equip it for life. The function of this soul is the use of nourishment and generation, or reproduction. Generation is the most natural function, as it is a means for a living being to participate in the future (the “everlasting and divine”) by producing something else of its own sort.
The use of nourishment allows the being to preserve itself, only existing while it is nourished. Nourishment allows an organism to grow as well as decay, according to its form. Since all living things possess the nutritive soul, all living things have the capacity for self-nourishment, growth, decay, and for reproduction. Further, since all nourishment involves digestion, and digestion involves heat, all beings contain heat (Aristotle, De Anima 415-416). The sensitive, or perceptive soul, distinguishes plants from animals.
Perception is a type of alteration, in that a suitable sense-organ in perception is affected or changed by an external object. The external object acts as the agent, possessing the qualities in actuality that the sense-organ possesses potentially. Aristotle describes that it is through an intermediate condition, such as air, that sense organs receive the forms or qualities of the objects of perception, not the matter, when involuntarily acted upon by the external object. Thus, the sensitive soul has the capacity to receive sensible forms, resulting in perception.
The sense-organs become like the agent after being affected, or receiving the qualities (Shields). Again, we can see Aristotle returning to his theory of Hylomorphism in describing perception as the change in the sense-organ as a result of the acquisition of form. The potential of the sense-organ is made actual in virtue of the external object which possesses the form in actuality. Aristotle states that every animal has the sense of touch, but not all possess the sense of sight, hearing, taste and smell.
Animals are further distinguished along these lines; while each possesses a nutritive and a sensitive soul, there are various degrees of complexity of the latter soul corresponding to the activities of the animal. Aristotle continues further that the possession of the perceptive soul implies that the animal has the capacity to desire, and desiring includes appetite, emotion, and wish. He also determines possession of this soul entails the ability to feel pleasure and pain and it is in virtue of this soul that some animals possess the power of locomotion (Aristotle, De Anima 413-415).
The rational soul, perhaps the most difficult section to interpret of De Anima, is essential and indicative of humans alone. It is in virtue of the rational soul, the intellect, that we come to know and understand things. The intellect is the seat of thought and thus reason. Thinking is similar to perception, as it involves the reception of form by a suitable capacity. However, while the object of perception is external and is the composite of form and matter, the object of thought is within the soul and is form alone (Shields).
While hard to follow, I believe the objects of thought are the forms of forms; they get their intelligible forms in virtue of the sensible forms sensed in perception. Aristotle discusses the concept of “appearances”, which are different from perceptions and beliefs, for appearances exist while we sleep, with no external stimuli actualizing the ‘sensation’, and beliefs involve conviction, while appearances do not. Appearances are images resembling objects of perception (Aristotle, De Anima 428). It is helpful to think of appearances as the representation of reality we see in imagination.
I believe Aristotle is claiming that it is these appearances that are the objects of thought. In intellection, the mind is made to be like the object of thought through reception of its intelligible form. The intellect is pure potentiality, it potentially has all of these objects of thought, and only in thought do these intelligible forms become actualized in the mind (Shields). As Aristotle’s philosophical worldview rests on a Hylomorphic principle, it is difficult to see how the alteration, bringing the intellect from potentiality to actuality in thought, comes about.
In perception, this is in virtue of an external object that acts as an agent for change in the sense-organ. But what is the agent of change in intellection? Aristotle divides the intellect into the active and passive intellects. The active intellect acts as the agent of change; when the mind thinks the active intellect actualizes the intelligible forms in the passive intellect. The passive intellect stores the concepts of knowledge and intelligible forms in potentiality, to be recalled by the active intellect during thought.
This means however, that the actual must precede the potential, contrary to what was discussed above. The nature of the active intellect is its activity, so it must be unremittingly active in order to cause the passive intellect to act and us to have thoughts and reason. If it is continuously active, this part of the rational soul must be eternal and thus stands in stark contrast with the rest of the souls Aristotle posits, but this controversial point is something I will not take up in this paper (Shields).