Aristotle definition of the soul in De anima (2005)

After gaining insight from the previous definitions of the soul given by his predecessors, Aristotle carefully designed his own comprehensive definition of the soul. According to his first intuition, the soul is "the principle of all animal life" (402a). After further exploration, he concludes that it is "the first actuality of a natural body having in it the capacity of life" (412a). In this paper, I will analyze Aristotle’s definition of the soul given in De anima by exploring his concepts of potentiality and actuality and his skillfully crafted examples of these terms and their differences. In the process, I will also explain Aristotle’s view of the soul as the set of hierarchical capacities and functions that an organism contains, and why it is catalogued as first actuality. Finally, I will elucidate how the interaction between the body and the soul works based on Aristotle’s line of reasoning, and provide my overall evaluation of the argument.

Aristotle approaches the intricate puzzle of the soul by establishing three types of substances, or existent things (412a). On the first level, there is matter, a physical manifestation that serves as the foundation for the other substances. Aristotle calls this mere potentiality, as the matter has the latent capacity of becoming alive. The next level is the form, which Aristotle calls first actuality. The final substance is the second actuality, a level at which form and matter engage in collective action to successfully perform a function. Aristotle used the axe as a metaphor in order to elucidate the differences between these two concepts. Potentiality corresponds to having all the materials needed to build an axe. The axe therefore has the potential to gain an identity, but has not done so yet. Moreover, first actuality is analogous to the axe being properly configured and gaining an identity that possesses latent capacities and functions that are waiting to be discovered. Finally, second actuality relates to the axe actually being used to cut. Interestingly, Aristotle finds these concepts in all things, independent of them being alive or not.

The second example used by Aristotle is the eye, a bodily part that is very familiar to all of us. The matter of the eye as an organ lies in its physiological components, the pupil, retina, cones, and cornea, among others. The form of the eye, according to Aristotle’s conceptual hierarchy, would be when these components gain an identity and have the dispositional capacity of eyesight. The eye is now constituted appropriately in such a way that it has the capacity of perceiving light and interpreting it into electrical signals. Thirdly, the full actuality would come into play when the eye activates its functions and actually sees, complementing the matter and the form. It is important to note that the first actuality can exist without the second actuality, in the same way that matter could exist without being organized. In other words, the fact that the components of the eye are present does not imply that the eye will gain its identity, and furthermore, if the eye exists as an organ, it does not necessarily have to see. However, it is important to note that Aristotle specifies that this example is only valid "if the eye were an animal" (413b). The existence of the eye is intricately connected to other body parts, and without them its survival is questionable. We can learn from this analogy that the eye does not have a soul because its existence is dependent of the organism, and it lacks independent qualities such as desire and direct nutrition.

Aristotle built on all of these concepts to apply them to his definition of the soul. For him, the body is mere potentiality; it contains all of the functional parts and is potentially alive. In order for the body to be actually alive, it needs the soul, which he considers to be first actuality. This reveals Aristotle’s belief that the body is intricately connected with the soul. Moreover, the soul is the body’s capacity to engage in activities that are characteristic of living things of its sort. However, for Aristotle’s not all organisms activate all of these functions, and thus there are different levels of employing the soul. Based on this pivotal idea, the philosopher proceeds to explain each of the latent capacities that lie in the soul by establishing a hierarchy in which each has the previous capacity as a foundation. As he explains, "some living things posses all [the powers of the soul], others some, others again only one" (414a).

The basic quality of the soul for Aristotle is nutrition, the ability to nourish itself. He argues that because of this quality, there is growth, decay, and reproduction. Aristotle argues that plants only posses this type of capacity. To posses this faculty, it is essential to have a soul as "nothing is nourished unless it possesses life" (416b). The next level is sensation, or perception, of which tactile sensation is essential. Due to this quality, the feeling of pain and pleasure arises. Aristotle catalogues animals as having this capacity. In order for a soul to have sensation, nutrition must be present as well. In other words, if sensation is a characteristic of that soul, its nutritive faculty is implied. The next capacity that can be developed is appetency, which is very closely related to sensation. After the soul is able to feel, there is a surge of desires, some which go along with physical needs, such as thirst and hunger, and other that do not, such as emotions like anger. The next step in the hierarchical ladder is locomotion, which involves movement from place to place as well as rest. Once again, in order to have a capacity, it is essential to possess the previous ones, building upon the hierarchical scheme. For locomotion to be possible, appetency, sensation and nutrition must also be present. The final level is understanding, which Aristotle believes to be the most uncommon. This entails reasoning using thought and intellect. In this category, human beings would presumably be found, even though he could argue that some are led only by imagination and not intellect. Once again, to posses this quality, all of the previous ones must be present. As Aristotle previously argued in Book I, having a mind does not mean you are intelligent. However, to be intelligent, you need a mind (404b).

This hierarchical organization set up by Aristotle leads to further interpretation. Does this mean that there are different degrees of souls, or are they equal? We could answer this question based on Aristotle’s concept of actuality and the assumptions upon which his concept of the soul is established. First of all, Aristotle argues that all of which is alive has a soul, and therefore, it possesses at least one of the capacities he describes. Furthermore, if he defines the soul to be of first actuality, which implies that it’s a set of not-yet-activated functions, all souls would be equal if they posses this set of functions, even though they may never get to develop all of them. However, this is not the case. Aristotle enumerates different types of souls depending on the functions which the living entity has developed. The first type of psyche, or soul, is the nutritive soul (424a). This is the type of soul which plants contain. This categorization is based on Aristotle’s idea that plants don’t have perception, because perception involves more than affecting the matter. Even though a heated iron can affect the plant, this does not mean that the plant perceives its touch. As Aristotle points out, "plants have no sensation, although they have one part of soul and are in some degree affected by the things themselves which are tangible" (424a). The next type of soul is the sensitive soul. This is characterized by possessing perception, and belongs to all animals. Finally, Aristotle describes the rational soul, which human beings possess. Unfortunately, he does not expand upon this type of soul in Book II.

Aristotle’s definition attempts to solve the enigma of the interaction between body and soul, which he believes his predecessors were unsuccessful at solving. After understanding Aristotle’s concept of actualities and the different types of souls, we should be prepared to understand the initial claims made in the second chapter. He describes the soul as an entity by which "we live, perceive, and have understanding" (414a), but it does not exist in the material level. He goes further by arguing that "the soul does not exist without a body and yet is not itself a kind of body" (414a). This clearly exposes the inseparable relation between these two units. The soul is not by itself a body but it belongs to one, and because of this it has to exist within a body. In other words, the soul needs the body in order to survive. Because of his remarks on Book II, Aristotle’s understands that the soul is inseparable from the body. This is in direct contradiction to previous Greek thinkers such as Socrates and Plato.

On one hand, Aristotle does not pursue a purely materialist conception of the soul, which some of his predecessors defended, where the soul is exclusively regarded as a physical unit on the same level as the body, and which can thus be explainable using atoms. The materialistic outlook dictates that the functions are dependent on the form. Yet, for Aristotle, the anatomy of the body should not be necessarily a limitation to its functions. For instance, Aristotle does not view emotions or desires as being a direct result of the form, as not all that has nutrition must also have desire. Furthermore, we can interpret that Aristotle believes that as you go further in the hierarchy, the qualities become more and more independent of the form. On the other hand, Aristotle does not follow the dualist conception either, where the soul is conceptualized as temporarily inhabiting the body. Aristotle retains Plato’s Theory of Forms, although he believes that he eliminated its impurities.

I consider Aristotle’s observations to be very valuable as they show his ability to be astonished at the world around him. The point where I initially differ with him is where he ties all his observations. Initially, I believed that without much argumentation he concludes that the soul is inseparable from the body, which I believe not to be true. However, reviewing Book III enriched my understanding of his theory. Interestingly, Aristotle revisits his concept of separability of the soul by contemplating the possibility that the intellect, being a quality that is not as dependent from the body, might be able to separate from the body, perhaps after death. Aristotle fails to explore this in great detail, but he implies that there might be a universal intellect that is undisturbed by material processes and ties all souls. We might come to understand his perception of the intellect as having some foundation on physical observation, which implies that it did not exist before birth, but which can eventually gain independence from the body. This notion opens up a door to a whole new realm of knowledge as Aristotle’s thoughts evolve.

Aristotle carefully evaluated the previously established notions in order to "accept whatever is correct in their views and avoid whatever is mistaken" (403b). Therefore, Aristotle does not aim at proving their theories as erroneous, but at reaching a harmonious and encompassing theory that would explain his clever observations of the world around him. It was also very wise that he chose to first evaluate the theories of his predecessors before rushing and stating his own. In this process, he reached valuable insight, and discovered unexplored paradoxes such as the "Third Man," which he tried to resolve. His theory seems to establish a solid consensus between the previous ones. Aristotle is successful in creating a thought-provoking theory that provides a good contrast to both the dualist and materialism conceptualization, and which served future philosophers to engage in deeper levels of understating of the nature of the soul.

Aristotle. De anima. Trans. R.D. Hicks. Amherst, NY: Prometheus Books, 1999. 9-72.