Teleology of Aristotle

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Teleology of Aristotle

Biology and Physiology. Aristotle applied his ideas of dunamis and immanent teleology most successfully in his works on biology and physiology. These subjects account for the largest share of his extant writings, in fact, and include such important texts as History of Animals, Parts of Animals, Movement of Animals, Generation of Animals, and the group of essays known as the Short Natural Histories or ParuaNatu-ralia. These volumes, all of which were written sometime around 335 b.c.e., exhibit Aristotle’s best balance between theory and observation.

Specimens. His research on plants and animals is indeed remarkable for its depth of detail and empirical rigor. These qualities were generally lacking among the earlier Greek scientists, who tended to devote themselves more to theoretical speculation than to observation and experiment. Relying on specimens gathered widely throughout the known world, however, Aristotle himself distinguished more than five hundred different species of animals, performed frequent dissections, and made precise records of anatomical descriptions. His discussion of unusual features of the placenta of a species of dogfish, for example, was finally verified in the middle of the nineteenth century. All of this highly detailed work was accomplished without the aid of any modern instruments such as the magnifying glass and microscope. The overall system of zoological classification (taxonomy) he constructed remained in effect until the great Swedish biologist Linnaeus in the eighteenth century.

Reproduction. Aristotle’s investigations in this field were not limited to anatomy and classification, however, but also ranged widely and deeply over physiology, nutrition and growth, locomotion, sensation, and reproduction. With reference to this last topic, Aristotle used rigorous logic to reject the idea of pangenesis. Most of the Hippocratic medical writers had believed that in both plants and animals, the seed draws its material from the parent’s whole body. Aristotle proposed instead the idea that the male parent supplies the formal and the efficient cause of the offspring, whereas the female contributes only the matter. This approach was consistent both with his theory of four causes and with his sexism as well.

Nutritive Soul. Aristotle was also deeply interested in the variety of living creatures in nature and what accounted for the differences among them. In History of Animals and especially in On the Soul (circa 335 b.c.e.), he identified the soul of a living creature with its formal cause, in the belief that form is what provides each thing with its true definition and essential characteristics. For Aristotle, the entire natural world is a vast hierarchy of different types of souls. Plants have what he termed a nutritive soul, which is the cause of their growth, nourishment, and reproduction.

Sensitive Soul. According to Aristotle, animals are superior to plants because, in addition to a nutritive soul, they also have a sensitive soul, which gives animals the ability to experience their surroundings. Among animals as a class, moreover, there is a hierarchy that runs from those that possess only one of the senses—clams, for instance—right up to the higher animals, which have all five. Aristotle also felt that the sensitive soul in animals that have all or at least most of the five senses gives them the power of locomotion. Since they can fully sense the world, they can also move toward what is good and away from what harms them.

Rational Soul. At the top of the hierarchy of earthly creatures come human beings. Along with the capacities of growth, nourishment, reproduction, sensation, and locomotion, people also have the higher capacity of reason. According to Aristotle, the rational soul makes reason possible.

Chain of Being. This graduated scale is indeed just one series of links in a much larger Chain of Being, which stretches from the lowest to the highest order of things, both inanimate and living. Here Aristotle used his theory of causes and his idea of immanent teleology as explanatory tools to connect all things in the universe into a single, systematic, comprehensive, and rational whole. At the same time, the hierarchical order of things in the world is reflected in a similar ordering of all the branches of science that study them.

Matter and Elements. At the lowest link in the chain is pure matter; it is the material out of which everything is made, but it lacks form and purpose. Next come the four elements (earth, air, fire, water), which Aristotle borrowed from Empedocles. Plato did the same thing, but whereas he went on to analyze the elements into abstract geometric entities, Aristotle reduced them to combinations of sensible qualities (hot/cold and wet/dry). Their character and behavior are completely determined by what Aristotle identified as their formal and final causes. It should come as no surprise that, even though they are inanimate, each of the four elements nonetheless still exhibits immanent teleology. Fire naturally moves up, for instance, away from the center of the world, while rocks move in the opposite direction. For Aristotle, this movement does not happen because of the force of gravity. In fact, the true nature of gravity was not fully appreciated for more than two thousand years after Aristotle, until Sir Isaac Newton formulated his famous law of gravitation in the seventeenth century. Instead, Aristotle believed the behavior of a falling rock must be explained in terms of its natural tendency to move downward. Because it is made of earth, it naturally moves toward the place where the greatest mass of earth is located.