Aristotle

A

Physics, or Natural Philosophy

In astronomy, Aristotle proposed a finite, spherical universe, with the earth at its center. The central region is made up of four elements: earth, air, fire, and water. In Aristotle's physics, each of these four elements has a proper place, determined by its relative heaviness, its “specific gravity.” Each moves naturally in a straight line—earth down, fire up—toward its proper place, where it will be at rest. Thus, terrestrial motion is always linear and always comes to a halt. The heavens, however, move naturally and endlessly in a complex circular motion. The heavens, therefore, must be made of a fifth, and different element, which he called aither. A superior element, aither is incapable of any change other than change of place in a circular movement. Aristotle's theory that linear motion always takes place through a resisting medium is in fact valid for all observable terrestrial motions. He also held that heavier bodies of a given material fall faster than lighter ones when their shapes are the same, a mistaken view that was accepted as fact until the Italian physicist and astronomer Galileo conducted his experiment with weights dropped from the Leaning Tower of Pisa.

B

Biology

In zoology, Aristotle proposed a fixed set of natural kinds (“species”), each reproducing true to type. An exception occurs, Aristotle thought, when some “very low” worms and flies come from rotting fruit or manure by “spontaneous generation.” The typical life cycles are epicycles: The same pattern repeats, but through a linear succession of individuals. These processes are therefore intermediate between the changeless circles of the heavens and the simple linear movements of the terrestrial elements. The species form a scale from simple (worms and flies at the bottom) to complex (human beings at the top), but evolution is not possible.

C

Aristotelian Psychology

For Aristotle, psychology was a study of the soul. Insisting that form (the essence, or unchanging characteristic element in an object) and matter (the common undifferentiated substratum of things) always exist together, Aristotle defined a soul as a “kind of functioning of a body organized so that it can support vital functions.” In considering the soul as essentially associated with the body, he challenged the Pythagorean doctrine that the soul is a spiritual entity imprisoned in the body. Aristotle's doctrine is a synthesis of the earlier notion that the soul does not exist apart from the body and of the Platonic notion of a soul as a separate, nonphysical entity. Whether any part of the human soul is immortal, and, if so, whether its immortality is personal, are not entirely clear in his treatise On the Soul.

Through the functioning of the soul, the moral and intellectual aspects of humanity are developed. Aristotle argued that human insight in its highest form (nous poetikos, “active mind”) is not reducible to a mechanical physical process. Such insight, however, presupposes an individual “passive mind” that does not appear to transcend physical nature. Aristotle clearly stated the relationship between human insight and the senses in what has become a slogan of empiricism—the view that knowledge is grounded in sense experience. “There is nothing in the intellect,” he wrote, “that was not first in the senses.”

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D

Ethics

It seemed to Aristotle that the individual's freedom of choice made an absolutely accurate analysis of human affairs impossible. “Practical science,” then, such as politics or ethics, was called science only by courtesy and analogy. The inherent limitations on practical science are made clear in Aristotle's concepts of human nature and self-realization. Human nature certainly involves, for everyone, a capacity for forming habits; but the habits that a particular individual forms depend on that individual's culture and repeated personal choices. All human beings want “happiness,” an active, engaged realization of their innate capacities, but this goal can be achieved in a multiplicity of ways.

Aristotle's Nicomachean Ethics is an analysis of character and intelligence as they relate to happiness. Aristotle distinguished two kinds of “virtue,” or human excellence: moral and intellectual. Moral virtue is an expression of character, formed by habits reflecting repeated choices. A moral virtue is always a mean between two less desirable extremes. Courage, for example, is a mean between cowardice and thoughtless rashness; generosity, between extravagance and parsimony. Intellectual virtues are not subject to this doctrine of the mean. Aristotle argued for an elitist ethics: Full excellence can be realized only by the mature male adult of the upper class, not by women, or children, or barbarians (non-Greeks), or salaried “mechanics” (manual workers) for whom, indeed, Aristotle did not want to allow voting rights.

In politics, many forms of human association can obviously be found; which one is suitable depends on circumstances, such as the natural resources, cultural traditions, industry, and literacy of each community. Aristotle did not regard politics as a study of ideal states in some abstract form, but rather as an examination of the way in which ideals, laws, customs, and property interrelate in actual cases. He thus approved the contemporary institution of slavery but tempered his acceptance by insisting that masters should not abuse their authority, since the interests of master and slave are the same. The Lyceum library contained a collection of 158 constitutions of the Greek and other states. Aristotle himself wrote the Constitution of Athens as part of the collection, and after being lost, this description was rediscovered in a papyrus copy in 1890. Historians have found the work of great value in reconstructing many phases of the history of Athens.

E

Logic

In logic, Aristotle developed rules for chains of reasoning that would, if followed, never lead from true premises to false conclusions (validity rules). In reasoning, the basic links are syllogisms: pairs of propositions that, taken together, give a new conclusion. For example, “All humans are mortal” and “All Greeks are humans” yield the valid conclusion “All Greeks are mortal.” Science results from constructing more complex systems of reasoning. In his logic, Aristotle distinguished between dialectic and analytic. Dialectic, he held, only tests opinions for their logical consistency; analytic works deductively from principles resting on experience and precise observation. This is clearly an intended break with Plato's Academy, where dialectic was supposed to be the only proper method for science and philosophy alike.

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