Eudemo di Rodi
Eudemo di Erasmo

Eudemo di Rodi - Filosofo greco (sec. IV aC). Allievo di Aristotele, insegnò probabilmente a Rodi. Scrisse una storia dell'aritmetica e della geometria e storie dell'astronomia e della teologia. A lui fu erroneamente attribuita l'Etica Eudemea, trasmessa fra gli scritti del maestro.

Le enciclopedie italiane non sono molto eudemoniche - non nel senso di felicità come scopo della vita, ma come informatrici circa Eudemo di Rodi - per cui più esaurienti notizie possono essere desunte dagli elaborati che seguono. Cominceremo con l'elencare i vari Eudemo della storia.

Magari l'Eudemo cui Erasmo da Rotterdam fa riferimento per il suo proverbio non compare assolutamente tra i vari Eudemo che troveremo, anche se esiste una possibilità che si tratti di Eudemo di Rodi.

Possiamo essere quasi certi che l'Eudemo di Erasmo non corrisponde a quello citato alcune volte da Eliano in La natura degli animali e corrispondente al secondo Eudemo elencato da William Smith. Ciò per due motivi. Innanzitutto Francesco Maspero, che ha tradotto quest'opera di Eliano (BUR, 1998), nelle note a pie' pagina scrive esplicitamente trattarsi di un autore sconosciuto; in secondo luogo - il che è più importante - perché tra le varie citazioni di Eudemo da parte di Eliano non compare il gallo. Per non ripeterci, le citazioni di questo misconosciuto Eudemo in Eliano corrispondono ai capitoli e ai paragrafi riferiti da William Smith.

Ma possiamo essere certi
che l'Eudemo di Erasmo è un errore!
Erasmo ha scritto Eudemo invece di Euelpide.
Infatti Euelpide o Evelpide (sperabene)
è uno dei personaggi degli Uccelli di Aristofane

I vari Eudemo
forniti da
Dictionary of Greek and Roman Biography and Mythology
William Smith, Boston, 1867

Eudemus of Rhodes

Eudemus of Rhodes (Εὔδημος) was an ancient Greek philosopher, who lived from ca. 370 until ca. 300 BC. He was the first historian of science. He was one of Aristotle's most important pupils, editing his teacher's work and making it more easily accessible.

Eudemus was born on the isle of Rhodos, but spent a large part of his life in Athens, where he studied philosophy at Aristotle's Peripatetic School. Eudemus's collaboration with Aristotle was long-lasting and close, and he was generally considered to be one of Aristotle's most brilliant pupils: he and Theophrastus* of Lesbos were regularly called not Aristotle's "disciples", but his "companions".

It seems that Theophrastus was the greater genius of the two, continuing Aristotle's studies in a wide range of areas. Although Eudemus too conducted original research, his forte lay in systematizing Aristotle's philosophical legacy, and in a clever didactical presentation of his teacher's ideas. Later authors who wrote commentaries on Aristotle often could made good use of Eudemus's preliminary work. It is for this reason that, though Eudemus's writings themselves are not extant, we know many citations and testimonia regarding his work, and are thus able to build up a picture of him and his work.

Aristotle, shortly before his death in 322, designated Theophrastus to be his successor as head of the Peripatetic School. Eudemus then returned to Rhodos, where he founded his own philosophical school, continued his own philosophical research, and went on editing Aristotle's work.

Eudemus was the first historian of science. At the insistence of Aristotle, he wrote histories of Greek mathematics and astronomy. Though only fragments of these have survived, included in the works of later authors, yet their value is immense. It is only because later authors used Eudemus's writings that we still are informed about the early history and development of Greek science. In his historical writings Eudemus showed how the purely practically oriented knowledge and skills that earlier peoples such as the Egyptians and the Babylonians had known, were by the Greeks given a theoretical basis, and built into a coherent and comprehensive philosophical building.

As regards his History of Arithmetics  we only have the tiniest bit of information: there is only one testimonium, saying that Eudemus mentions the discovery by the Pythagoreans that it is possible to connect musical intervals with integer numbers.

Eudemus's History of Geometry is mentioned by many more writers, including Proclus, Simplicius, and Pappus. From them we know that the book treated the work by, among others, Thales of Miletus, the Pythagoreans, Oenopides of Chios, and Hippocrates of Chios. Among the topics Eudemus discussed were the discovery of geometrical theorems and constructions (systematized in Eudemus's days by Euclid in his Elements), and the classical problems of Greek geometry, such as the quadrature of the circle and the duplication of the cube.

We know quite a lot too about Eudemus's History of Astronomy, from sources such as Theon of Smyrna, Simplicius, Diogenes Laërtius, Clement of Alexandria, and others. Building upon those data we can reconstruct with some accuracy the astronomical discoveries that were made in Greece between 600 and 350 BC, as well as the theories that were developed in that period regarding the earth, solar and lunar eclipses, the movements of the heavenly bodies, etcetera. Philosophers and astronomers treated by Eudemus include Thales, Anaximander, Anaximenes, Oenopides, Eudoxus, and others.

Two other historical works are attributed to Eudemus, but here his authorship is not certain. First, he is said to have written a History of Theology, that discussed the Babylonian, Egyptian, and Greek ideas regarding the origins of the universe. Secondly, he is said to have been the author of a History of Lindos (Lindos is a port on Rhodos).

To Eudemus is also ascribed a book with miraculous stories about animals and their humanlike properties (exemplary braveness, ethical sensitivity, and the like). However, as the character of this work does not at all fit in with the serious scientific approach that is apparent from Eudemus's other works, it is generally held that Eudemus of Rhodos cannot have been the author of this book (it may have been another Eudemus—Eudemus was a fairly common name in ancient Greece).

Eudemus, Theophrastus, and other pupils of Aristotle took care that the intellectual heritage of their master after his death would remain accessible in a reliable form, by recording it in a long series of publications. These were based on Aristotle's writings, their own lecture notes, personal recollections, etcetera. 

Thus one of Aristotle's writings is still called the Eudemian Ethics, probably because it was Eudemus who edited (though very lightly) this text. More important, Eudemus wrote a number of influential books that clarified Aristotle's works: 

Eudemus's Physics  was a compact, and more didactical version of Aristotle's homonymous work.

Eudemus wrote two or three books dealing with logics (Analytics and Categories (possibly the same book), and On discourse), which probably expounded Aristotle's ideas.

Finally, a geometrical work, On the angle.

A comparison between the Eudemus fragments and their corresponding parts in the works of Aristotle shows that Eudemus was a gifted teacher: he systematizes subject matter, leaves out digressions that distract from the main theme, adds specific examples to illustrate abstract statements, formulates in catching phrases, and occasionally inserts a joke to keep the reader attentive.


Ivor Bulmer-Thomas, 'Eudemus of Rhodes', in: Dictionary of Scientific Biography, Charles Coulston Gillispie, ed. (18 Volumes, New York 1970-1990) Volume IV (1971) pp. 460-465.  

F[ritz] Wehrli, 'Eudemos von Rhodos', in: Paulys Realencyclopädie der Classischen Altertumswissenschaft, G. Wissowa, ed. (51 Volumes; 1894-1980) Vol. Suppl. XI (1968) col. 652-658.  


Eudemus of Rhodes
Born: about 350 BC in Rhodes, Greece - Died: about 290 BC

Article by: J J O'Connor and E F Robertson
April 1999

School of Mathematics and Statistics 
University of St Andrews, Scotland

We should certainly credit Eudemus of Rhodes for his achievements in this archive since Eudemus seems to have been the first major historian of mathematics. Simplicius informs us that a biography of Eudemus was written by Damas, who is unknown but for this reference, but sadly no trace of this biography has been found. As exciting aspect of the history of mathematics is that the discovery of this text (and other lost texts) in the future, although highly unlikely, always remains a possibility.

Eudemus was born on Rhodes and we know that he had a brother called Boethus. Of his parents and early life we know nothing, but we do know that he studied with Aristotle. Aristotle spent time in Athens, Assos and other places and it would certainly be good to understand when Eudemus studied with him. Unfortunately there is no record either of time or of place which would let us answer these questions with any degree of certainty. W Jaeger, however, in his discussion of Aristotle [4] (see also [5]) has argued strongly that Eudemus studied with Aristotle during his period in Assos.

Aristotle had two followers, Eudemus and Theophrastus of Lesbos, who were known as his "companions". We should make it clear, however, that there was another philosopher called Eudemus associated with Aristotle, namely Eudemus of Cyprus and it was this other Eudemus after whom Aristotle named his famous text Eudemus. When Aristotle realised that he had only a short time left to live he chose his successor between his two companions, Eudemus and Theophrastus. He chose Theophrastus and it appears that Eudemus, although not unhappy with the decision, left Athens and set up his own school, probably back on his native Rhodes.

To say that Eudemus was not an original mathematician may be fair but just a little harsh, for we do know through Proclus that he wrote an original mathematical work called On the Angle. This work is lost so we are unable to judge its importance but it does seem likely to have been considerably less important than his works on the history of mathematics.

We know of three works on the history of mathematics by Eudemus, namely History of Arithmetic (two or more books), History of Geometry (two or more books), and History of Astronomy (two or more books).  

The History of Arithmetic is known to us from only one reference to it in the writing of Porphyry. This reference tell us that the first book dealt with the Pythagorean idea of number and its interrelations with music.

The History of Geometry is the most important of the three mathematical histories of Eudemus. Although the work has not survived, it was available to many later writers who made heavy use of it. We are fortunate therefore that much of the knowledge that Eudemus had of the history of Greek mathematics before Euclid (it had to be before Euclid given the dates when Eudemus was writing) has reached us despite the fact that he book has not. In many of the articles in this archive we have quoted from accounts based on Eudemus. To illustrate with one example, the work of Hippocrates on the quadrature of lunes is only known to us through Eudemus's History of Geometry.

It is unclear exactly when the History of Geometry was lost. Paul Tannery (see for example [7]) believed that it was lost before the time of Pappus while others such as J L Heiberg have argued that Pappus and Eutocius both wrote with an open copy of Eudemus's History of Geometry in front of them.

The History of Astronomy again was heavily used by later writers and in exactly the same way as his geometry text, much information has survived in the works of others despite the loss of the original text. In particular Thales' eclipse prediction was described in Eudemus's work and we believe that Eudoxus's system of concentric spheres was first described there and later transmitted to us through the writing of Simplicius in the second century AD. Other topics in this book included:

... the cycle of the great year after which all the heavenly bodies are found in the same relative positions; the realisation by Anaximander that the earth is a heavenly body moving about the middle of the universe; the discovery by Anaximenes that the moon reflects the light of the sun and the explanation of lunar eclipses; and the inequality of the times between the solstices and the equinoxes.

We have described above the important contributions of Eudemus to mathematics. However he is even better known for his contribution to saving the work of Aristotle for posterity. But for Eudemus we might not have had access to the works of Aristotle for he used his own lecture notes, Aristotle's lecture notes and recollections from memory to produce volumes of Aristotle's work fit for publication.

One further work is definitely due to Eudemus, namely a work on Physics which was a treatise in four books following the work by Aristotle of the same title fairly closely. Simplicius had a copy of this work which he found very helpful in understanding Aristotle's Physics and perhaps this was precisely the role the Eudemus intended for the work. Another work by Eudemus was on Logic, in fact he may well have written two logic books and he also wrote On Discourse.

Some works by Eudemus are harder to identify with Eudemus of Rhodes and may have been written by others with the same name. Certainly there are many references to a work on animals written by a certain Eudemus and one of the references certainly does refer to Eudemus of Rhodes. Since the work seems to have been a collection of fables about animals the subject matter seems too far removed from the serious, scientific and scholarly works which he certainly wrote. Perhaps more likely is a work on the poet Lindos. Since Lindos had connections with Rhodes the link makes this a more likely possibility.  

Again there is a reference which seems to imply that Eudemus wrote a history of theology and again this seems highly probable. Many authors refer to Eudemus as the 'pious Eudemus' due to his belief in the 'contemplation of God'. This however may be due to editing by a later Christian who would have seen that clearly Eudemus meant 'contemplation of God' rather than what is much more likely what he wrote 'contemplation of Mind' and "corrected" the text accordingly!