With the possible exception of Plato, Aristotle, 384-322 BC, is the most influential philosopher in the history of Western thought. Logic into the present century was basically Aristotelian logic. The study of the natural sciences was dominated by Aristotle until early modern times, and modern physics was developed in reaction to the Aristotelian tradition. His metaphysics continues to be the subject of philosophical debate, although his ethics now constitutes that part of his philosophy which appeals most to contemporary philosophers. Aristotle's influence extends far beyond philosophy, however. For example, Aristotle was the founder of biology; Charles Darwin regarded him as the most important contributor to the subject. Aristotle's Poetics, the first formal work of literary criticism, had a strong influence on the theory and practice of modern classical drama. Aristotle's immense influence is due primarily to the fact that he seemed to offer an all-encompassing system, which, although lacking in certain respects, was as a whole formidably imposing and unrivaled in its comprehensiveness.




Aristotle was born in 384 BC in Stagira in northern Greece. His father, Nicomachus, was a physician with close connections to the Macedonian court, which were maintained by Aristotle and by his school even after his death. It may have been his father's influence that gave Aristotle a strong interest in anatomy and the structure of living things in general, helping him develop a remarkable talent for observation.


In 367, Aristotle went to Athens to join Plato's Academy, first as a student, then as a teacher. Plato had gathered around him a group of outstanding men who worked in a wide variety of subjects, ranging from medicine and biology to mathematics and astronomy. They shared no common doctrine but were united by the systematic effort to organize human knowledge on a firm theoretical basis and expand it in all directions. This effort, more than anything else, characterizes Aristotle's own work.


It was also part of the Academy's program to train young men for a political career and to provide advice to rulers. Thus, after Plato's death, Aristotle joined (347) the court of Hermias of Atarneus, and later went (343) to the court of Philip II of Macedonia, where he became tutor to the young Alexander the Great. In 335, Aristotle returned to Athens to found his own school, the Lyceum, or Peripatus. Whereas the Academy had become rather narrow in its interests since Plato's death, the Peripatus under Aristotle and his successor, Theophrastus, pursued a wider range of subjects than the Academy ever had. In particular, prominence was given to the detailed study of nature. After the death of Alexander the Great in 323, anti-Macedonian feeling in Athens rose, and Aristotle retired to Chalcis, where he died the following year.




All Aristotle's writings for a larger audience, mainly dialogues, have been lost except for some fragments. What remains are treatises apparently meant for use within the school. These form the so-called Corpus Aristotelicum. In addition, there survives a mutilated version of his Constitution of Athens, some letters of doubtful authenticity, and some poems, including an elegy on Plato.


The Corpus Aristotelicum can be traced back to the 2d century AD. An earlier edition is said to have been prepared by Andronicus of Rhodes in the 1st century BC, but this is doubtful. In what form Aristotle's treatises were available before the 1st century BC is a matter of controversy. The texts of the treatises raise serious problems. Some of them so clearly contain later thought and language that they cannot possibly be by Aristotle; others are of doubtful authenticity. Even such clearly authentic writings as the Metaphysics show the work of later editors. Many texts show signs of addition and revision, and it is difficult to determine which of these were made by Aristotle himself. Attempts have been made--without much success--to reconstruct the original form of a text, to distinguish the different levels of revision it has undergone, and to associate these levels with phases in Aristotle's thought.


Underlying the order of the treatises in the Corpus is the traditional division of philosophy into logic, physics, and ethics. Two sets of Aristotelian writings do not easily fit this scheme, the Metaphysics, and the Rhetoric and the Poetics. These are appended to the physical and the ethical writings, respectively. Thus the following classification of Aristotle's writings is observed: (1) Logical writings--Categories, On Interpretation, Prior and Posterior Analytics, Topics, Sophistical Refutations; (2) Physical writings--Physics, On Generation and Corruption, On the Heavens, Meteorologica, On the Soul, Parva Naturalia, History of Animals, Parts of Animals, Generation of Animals, Motion of Animals; (3) Metaphysics; (4) Ethical writings--Nicomachean Ethics, Eudemean Ethics, Magna Moralia, Politics; (5) Rhetoric, Poetics.






Logic, the theory of formal truth and validity, originated in reflections on the practice of dialectic, the kind of debate found in Plato's dialogues. Dialogue was regarded as the appropriate form for philosophical arguments, and hence the acquisition of dialectical skill was regarded as crucial for students of philosophy. Aristotle's first great achievement was probably a handbook, now entitled Topics and Sophistical Refutations, in which he provided the first general analysis of dialectic and formulated rules for success in this kind of argument. Clearly, dialectical argument does not by itself lead either to incontestably true conclusions or to scientific knowledge. Dialectical method aims to ensure that premises are plausible and that arguments are valid. In the Prior and Posterior Analytics Aristotle tried to work out which kind of premises are needed to gain scientific knowledge and which formal conditions an argument must satisfy to be incontestably valid (see logic). According to the Posterior Analytics, the ultimate premises or principles of a science are necessary truths. Human knowledge of these truths is based on experience; it is not itself a matter of experience, however, but rather of reason. When a subject is sufficiently familiar, its governing principles become evident to reason. Deduction from these principles provides not only the knowledge that something is true, but also the reasons why it is true. For Aristotle, both are required for scientific knowledge.


Aristotle's ideal of a science as a deductive system based on evident axioms had a considerable influence on the history of science. In the Prior Analytics he examines the conditions an argument must satisfy in order to be incontestably valid. Because he is primarily concerned with the arguments whose propositions are scientific, and because he only regards general categorical propositions as scientific, his theory applies only to a small class of logically valid arguments, the so-called categorical syllogisms. Aristotle proceeds by specifying certain parts of an argument, or moods, that axiomatically count as valid. Any argument that can be transformed into an axiomatically valid argument must also be valid.


Natural Sciences


The natural sciences are concerned with natural objects that are characterized by the fact that they are subject to change. Change is therefore the basic phenomenon with which physics has to deal. Hence Aristotle's work in physics is devoted to an analysis of change and a discussion of its presuppositions. According to Aristotle every change involves three factors: (1) a feature or form that exists as a result of change; (2) the earlier absence of this form; and (3) the matter that was always there but which, as a result of the change, is now characterized by the form in question. In the case of a statue the three factors are the form of the statue; its previous lack of form; and the material from which it was made.


Aristotle ties the notions of matter and form to other notions. Thus he explains that if matter becomes an F the matter is F potentially (that is, is capable of being an F ), whereas the form is the actuality in virtue of which it is now an actual F. Matter and form are the material and the formal cause, respectively, of what comes to be. A cause is a factor, and a true statement about that factor helps to explain the being of what is caused. Aristotle distinguishes four kinds of causes. If a house comes into being, its efficient cause is the builder, its formal cause the structure by virtue of which it is a house, its material cause the matter that has received this structure, and its final cause the end or purpose for which houses exist, namely the protection of people and property. Because motion, due to its continuity, has no end, presupposes a location, seems to presuppose a void, and takes time, Aristotle also discusses these notions in detail. He denies the existence of a void and considers the continuity of motion at length. Finally, he argues that there would be no motion at all unless there is first a force of movement that is itself unmoved--namely God.


The form of an object helps to account for its behavior. Aristotle calls the forms of living things "souls," which are of three kinds: vegetative (plants), sensitive (animals), or rational (human beings). Because Aristotle believed that the soul is merely a set of defining features, he did not regard the body and the soul as two separate entities that mysteriously combine to form an organism. Hence it is not clear what he had in mind when he described an active intellect whose activity is presupposed by the activity of the human mind and that is supposed to be able to exist independently of the body.


Most of Aristotle's work in biology was devoted to zoology. In Aristotle's study of biology the doctrine of teleology is particularly prominent. This doctrine, that the form of natural objects is determined by their final ends or purposes, has frequently been misunderstood as an assertion that there is a universal design in nature. Aristotle simply insists that the structure and the behavior of things also has to be understood as contributing to their individual being and function.




Whereas sciences deal with particular kinds of beings, metaphysics is concerned with beings as such. According to Aristotle there is no such thing as mere being; to be is always to be a substance or object, a quantity, a quality, or a member of some other basic category. Substances are prior to nonsubstances because qualities or quantities are determined by substances. Such substances as God may, however, lack quantities and qualities. Hence an account of beings is, in the first place, an account of substances. Initially, it appears that substances are objects, like the everyday objects, but closer consideration shows that the primary individuals are the forms or essences of particular objects. To understand these it is necessary to realize that they are a particular kind of substance--embodied substantial forms. To understand substance, therefore, it is necessary to consider immaterial substantial forms, ultimately God. Only then can humans understand what it is to be a substance, and what it is to exist. Ultimately, then, the study of metaphysics becomes in part theological.




The end, or good, of humankind is not merely to live, but to lead a good, flourishing life that manifests the rational nature of humanity and thus satisfies human needs. The pursuit of happiness is a search for the good life, which is composed of virtuous actions. Aristotle offers no simple definition of goodness, but he advises that virtue is a mean, lying between extremes. Generosity, for example, consists in giving neither too little nor too much. Aristotle also describes intellectual virtue and moral virtue, which correspond to the rational and the irrational parts of the soul. The most important of the intellectual virtues are theoretical and practical wisdom. To the extent that the irrational part of a person's soul is subject to reason and has reasonable desires and feelings, that person is characterized by such moral virtues as justice, courage, and magnanimity. The effort to perform virtuous acts creates the desire to do the right thing for its own sake and also cultivates practical wisdom. The highest, and therefore most satisfying, form of rational existence is a life of contemplation--the exercise of the theoretical wisdom. Because human beings are not purely rational, however, a flourishing, happy human life demands the exercise of both the intellectual and the moral virtues.


Humans are by nature gregarious and are disposed to form political associations to fulfill their desires. The aim of the state is the good life of its citizens. In the Politics, Aristotle evaluates different forms of government in the light of these assumptions. His views are profoundly influenced by the belief that only certain people are endowed with the capacity to lead the good life and undertake the responsibilities of citizens, and that fewer still are capable of holding public office. Thus a Greek democracy (which was nonrepresentational and in which offices rotated) imposed severe limitations on rights to citizenship. Aristotle believed that a state should be organized in such a way as to encourage that part of the population which is capable of the good life to practice moral and theoretical virtue.


Rhetoric and Poetics


In their competition for bright, ambitious young men, the Greek schools of philosophy were not willing to allow specialists, such as Isocrates, to monopolize instruction in rhetoric and oratory . Aristotle in his Rhetoric makes use of traditional rhetorical methods, but he deals with the subject in a more systematic and theoretical fashion. Priority is given to the orator's ability to invent arguments, to see what is plausible in a given case. Only then does Aristotle turn to the strategy and verbal form of the plea.


In the Poetics, Aristotle defends poetry against Plato's criticisms. Whereas Plato had spoken of the imitative character of the arts, Aristotle regarded the poet's creations as imaginative, ideal truths closer to reality than the records of historiography. He also rejected the view that poetry should be judged by the morality of what it depicts. The interpretation of Aristotle's observation in the Poetics, that tragic drama, by engendering pity and fear, can purge the emotions, has always been disputed.




During the Hellenistic period the Aristotelian tradition was continued by the Peripatetic school (see Peripatetics). Because of the eclecticism and neoclassicism that arose during the 1st century BC, Aristotle became an authority for all philosophers, especially in logic and in natural sciences. The leading philosophy from the 3d century AD onward, however, came to be Platonism, which better suited the religious temperament of the age. As a result theologians, whether in western Europe, in Byzantium, or in the Islamic states, tended to be Platonists and to view pure Aristotelianism, as represented by the Arab commentator Averroes, for example, as heretical. Nevertheless, the history of scholastic philosophy (see scholasticism) is primarily the history of the assimilation of Aristotelianism despite the opposition of theologians. It was because of the close association of Aristotelianism and scholasticism that Aristotelianism fell into disrepute in early modern times. During the 19th century, however, Aristotelianism was revived in reaction to Hegelianism.


Michael Frede


Bibliography: Allan, D. J., The Philosophy of Aristotle, 2d ed. (1970); Barnes, Jonathan, ed., The Cambridge Companion to Aristotle (1995); Cooper, J. M., Reason and Human Good in Aristotle (1975; repr. 1986); Grene, Marjorie, A Portrait of Aristotle (1963; repr. 1979); Irwin, Terence, Aristotle's First Principles (1989; repr. 1990); Jaeger, Werner, Aristotle (1948; repr. 1983); Ross, W. D., Aristotle (1923).

Last modified on: Friday, October 17, 1997.