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(b. Eresus, Lesbos, ca. 371 b.c.;d. Athens, ca. 287 b.c.)

botany, mineralogy, philosophy.

Theophrastus was associated with Aristotle for more than two decades and succeeded him as head of what came to be known as the Peripatetic school. According to one report (Diogenes Laërtius V, 36), he studied under Plato before joining Aristotle. It is likely that he met Aristotle in Asia Minor (347) or on Lesbos (344–342), went with him to Macedonia (342–335), and then to Athens when Aristotle returned and began to teach in the Lyceum (335). When Aristotle retired to Chalcis shortly before he died (322), Theophrastus became the leader of the scholars and students who had met with Aristotle at the Lyceum.

During his tenure of thirty-five years Theophrastus had two thousand students, among them the physician Erasistratus and the philosopher Arcesilaus. So well was he regarded by the Athenians that an attempt to prosecute him for impiety failed and a restrictive law against him and other philosophers was repealed. On his death he bequeathed the school’s property jointly to ten relatives and associates. To one of these, Neleus, he left the library, which would have included not only his own writings and those of Aristotle but also, presumably, the collection of others’ writings made by Aristotle and himself. The provisions in his will for repairs to the property, for the use of it by a few friends, and for the disposition of the books suggest that the school had suffered in the tumult through which Athens had passed in the years before his death and that he regarded its future as uncertain. (On the transmission of the Peripatetic texts, see “Aristotle: Tradition and Influence,”)

The Hellenistic lists of Theophrastus’ writings contain over two hundred titles that cover not only the various branches of science and philosophy but also history, law, literature, music, poetics, and politics. Even if there belong to parts of longer works, and if some titles belong to parts of longer works, and if some are incorrectly ascribed, it is nevertheless evident that Theophrastus was a man of remarkable learning and industry. From his writings there remain only two longer works on botany, a few short treatises on science, an essay on metaphysics, the Characters, and fragmentary excerpts and paraphrases in the works of later writers. In length the two botanical works are about double the remainder.

From such meager and unbalanced evidence a uniform account and just assessment of Theophrastus’ scientific accomplishments are impossible. He has generally been considered a botanist whose contributions in other fields were secondary to those of his teacher. His dependence on Aristotle may have been distorted by the transmission of the texts; several of the shorter treatises, notably the Metaphysics and De sensibus, are found in manuscripts with the longer works of Aristotle on the same subjects, and many of the fragments of lost works are in later Greek commentaries to Aristotle, thus giving the impression that his work was little more than an appendix.

Recent scholarship (Regenbogan and Steinmetz) has done much to correct this impression, but it is doubtful that an exact line can be drawn between the contributions of the two men. Their fundamental agreement is evident from their writing, but it does not follow that their long association was that of teacher and student. That, even when disagreeing, Theophrastus does not mention Aristotle by name is probably a sign not merely of respect but also of his assumption of responsibility for their work as a whole. The books that Neleus inherited from Theophrastus were a Peripatetic corpus. Apparently there was no systematic attempt to divide the works by author until catalogs were made toward the end of the third century b.c.; and even after the editions of Andronicus of Rhodes in the first century b.c., doubt remained. Within the works attributed to Aristotle in antiquity, modern scholars have not only discerned the influence of Theophrastus but also have identified some treatises as partly or wholly his. Questions of authorship are beyong the cope of this article. If in what follows differences are stressed, they should be regarded as due to a continuing process rather than to a radical change in attitude or method.

A further problem in an account of Theophrastus is the state of the preserved evidence. The latest general edition of his work (Wimmer) is based on incomplete knowledge of the manuscripts and fragments, and few of the individual works have received detailed study. It seems best to confine this article to a few works that are accessible in more recent editions with commentary and scholarly translation.

The general trend of Theophrastus’ thought is shown by the Metaphysics. In the main he does not deviate from Aristotle’s assumptions but, rather, points out the difficulties in their application. Thus he agrees that reality is divided into the intelligible and the sensible and that the intelligible cause of the sensible world is an unmoved first mover that causes motion by being the object of desire. But, he asks, if there is only one such mover, why do all the heavenly bodies not have the same motion? Why does desire not presuppose soul and, therefore, a psychical motion better than rotation? Why is rotation limited to the heavenly bodies and shared only incidentally by the sublunar region? If motion is as essential to the heavenly bodies as life is to living things, does it need any explanation (7–11, 27–28)?

With regard to teleology, too, Theophrastus has doubts. He accepts the general principle that nature does nothing in vain, but he questions its applicability. In the heavens, and still more in the terrestrial region, some things seem to be due to coincidence or necessity. What purpose is served by the incursions and refluxes of the sea or by the birth and nutrition of animals–let alone by such superfluous things as the breasts of males or such positively harmful things as the horns of deer? If, he says, nature does desire what is best, most things are recalcitrant; even among animate things, which are a small part of the universe, there are few for which existence is better than nonexistence (15, 28–32).

In the Metaphysics, Theophrastus offers no new or conclusive answers to the problems raised–nor is there evidence that he ever did. He does, however, suggest a way of dealing with the phenomena alone. We should perhaps conceive the unity of the universe to be that of a system the various parts of which are fitted together in the greatest possible harmony but differ in the degree to which they possess order, the heavenly bodies possessing more and the sublunar region less (16, 34). Hence there must be different kinds of knowledge, and each kind must use a method appropriate to its object: there must be different methods for the objects of reason; for primary natural objects; and for secondary natural objects, such as animals, plants, and inanimate things (22). When we advance to first principles, we contemplate them with the mind; but the starting point in our search for causes is sense perception, which observes differences among its objects and supplies material for thought (19, 24–25). This emphasis on the differences among objects and methods of knowledge, and on the need to start from observation of the particular, is characteristic of Theophrastus’ scientific works as a whole.

On the nature of the primary material substances, Theophrastus accepted Aristotle’s theory of four qualitatively distinguished simple bodies. In the introductory sections of his De igne, however, he gives a penetrating criticism of the theory. Comparing fire with the other simple bodies, he makes several observations that cast doubt on its status as an elementary substance: the other simple bodies change into one another but cannot generate themselves, but fire both generates and destroys itself; the ways in which fire is generated are for the most part violent; fire is generated in many different ways, but the other simple bodies are generated only by natural change into one another; moreover, these other simple bodies exist by themselves, but fire requires fuel as a substrate and is destroyed when the fuel has been exhausted (1–3).

The last objection is the most serious; if fire cannot exist without fuel, it cannot rightly be called a primary substance or principle, since it is neither simple nor prior to its substrate (4). Theophrastus considers several possibilities: that the first sphere is pure and unmixed heat, that celestial and terrestrial fires are different in kind, and that the sun is a kind of fire. He appears inclined to view heat rather than fire as a principle, for, he says, heat is more widely distributed than fire and is more influential in natural processes. He comes to no conclusion but instead notes further difficulties. If heat is always bound up in a substrate, it appears to be an affection of something else and not a principle. If it is objected that fire cannot exist independently, the same may be said of all the simple bodies, since they are all compounds and are reciprocally involved (8). As he recognizes, his discussion of fire has led to larger questions about the nature of causes.

Theophrastus declines to attempt answers to the larger questions, and in the main part of De igne he concerns himself with terrestrial phenomena of fire. His topics include not only such central matters as the generation, preservation, and extinction of fire but also such farfetched examples as the quenching of fire by salamanders, the melting of coins in the belly, and the jumping of grain on Babylonian threshing floors. In short, he excludes nothing that seems, or is said, to be connected with fire and heat.

In some explanations he relies on two Aristotelian concepts, the interaction of opposites and antiperistasis (the concentration of one thing by another). By the former he explains the generation and destruction of fire: fire is nourished by moist fuel but is destroyed by an excess of moisture of cold, or by a greater fire (10–11, 20, 26–27). By the later he explains why, in cold weather, fires burn more rapidly, baths are warmer, and our bodies are stronger (12–13, see also 14–18), and why fires are extinguished by excessive compression (11, 58). The difference between the two concepts is that the latter assumes that the qualitative opposites are stable and that the greater does not assimilate the lesser, as it does in combustion. This assumption runs through much of the treatise. He speaks of fire, heat, and flame as if they were composed of discrete particles having different degrees of fineness; and he explains interaction by the symmetry or asymmetry between the particles of one substance and the pores of another (for instance, 42). In so doing he appears to abandon the theory of qualitative elements and return to the pre-Socratic effluence-pore theory. It is clear, however, that the particles are not Democritean atoms, for interaction requires both the appropriate size of particles and pores and the qualitative difference between the substances. Theophrastus has not arrived at a new theory about the essential nature of fire as an element. He has, rather, demonstrated that, as Aristotle had said (Meteorologica, 340b21–23), the fire of our experience is different from elemental fire and that the various phenomena associated with it do not have a single explanation. It remained for his successor Strato to formulate a Peripatetic atomism.

Among the extant writings Theophrastus’ monograph on petrology, De lapidibus, best illustrates his investigation into inanimate compounds of the elements. In this, along with several other works known only from fragments and references, he carries forward the detailed investigation proposed by Aristotle at the end of MeteorologicaIII . His theoretical basis is the classification already made by Plato and adapted by Aristotle: metals are composed of water, and stones and mineral earths are composed of earth (1). On this basis he gives a brief description of the processes by which stones and mineral earths are formed (2–3); their matter is earth that had been purified and made uniform through conflux or filtering or some other kind of separation; the purity and uniformity of the matter determines such qualities as smoothness, density, luster, and transparency; solidification of the matter is due in some cases to heat and in others to cold–although it might seem that all things composed of earth are solidified by heat, since solidification and dissolution are contrary processes.

By thus admitting that heat and cold may have the same effect, Theophrastus recognizes that the classification, as simply stated, is not adequate to account for the diversity of the phenomena. Just as metals are solidified by cold and dissolved by heat, stones and earths ought to be solidified by heat and dissolved by cold; but in fact some stones, such as metal-bearing ores, are dissolved by heat (9). It is noteworthy, too, that although he apparently intends conflux and filtering to account for some distinctive differences between formations (deposits and veins have been suggested by Eichholz), he makes only two inconclusive references to them when he turns to specific instances (50, 61).

The body of the work is a systematic discussion of stones (3–47) and mineral earths (48–69) found around the Mediterranean and in the farther regions traversed by Alexander’army. Substances are distinguished by visual and tactile qualities and by their behavior, particularly in reaction to fire (9–19). Included are the earliest known Greek references to the use of mineral fuel (16), the pearl (36), the touchstone in testing alloys (45–47), and the manufacture of white lead (56). Of particular interest for the history of technology are the accounts of the preparation of pigments (50–60) and the uses of earths dug from pits (61–69).

Theophrastus’ purpose is not to give an exhaustive treatment of the subject but to illustrate differences between types and to record unusual cases for further investigation. His descriptions are for the most part brief and restricted to what is readily observable, and he omits many substances that must have been familiar (his list is only one-tenth that of Pliny). How much Theophrastus knew from his own observation is questionable. He probably did not collect specimens systematically or conduct experiments. He frequently makes it clear that he is relying on written documents or hearsay; he has not always observed what he reports as fact, as is shown by his statement that the pearl is transparent. His reliance on the reports of others leads him to treat seriously what might seem too fantastic even for mention, such as stones formed by the urine of the lynx (28) and pumice formed by sea-foam (19,22). Such instances underscore the factual limitations of Theophrastus’ work, but they do not detract from its historical significance. It is the first methodical study of mineralogy and the only one before Agricola’s in the sixteenth century that considers mineral substances for themselves rather than for their curative or magical properties.

Theophrastus’ works on botany correspond to Aristotle’s Historia animalium and De partibus animalium; in Historia plantarum he is concerned with description, classification, and analysis, and in De causis plantarum , taking the tree as his standard, he deals with general matters: permanent and annual parts and their composition; classification into tree, shurb, undershrub, and herb; general and special differences in the plants as wholes and in their parts. From this Theophrastus proceeds to particulars; book II , domesticated trees, their propagation, and their care; book III , wild trees: book VI , undershrubs; books VII and VIII , herbaceous plants. Included are three books on special topics: book IV , trees and plants peculiar to certain regions; book V , woods and their uses; book IX , plant juices and medicinal herbs. The main subjects of De causis plantarum are the following: book I , generation and propagation, sprouting and fruiting; book II , effects of natural factors; book III , effects of cultivation; book IV , seeds; book V , alteration, degeneration, and death; book VI , plant juices. (The treatise De odoribus and the lost treatise on wine and olive oil may originally have followed book VI .)

Within this framework Theophrastus describes and discusses some 550 species and varieties, extending geographically from the Atlantic through the Mediterranean littoral and as far east as India. Among his literary sources he cites poets, philosophers, and scientists from Homer to Plato (notably Empedocles, Menestor, and Democritus among the pre-Socratics who had written on plants). He makes frequent references to the beliefs and practices of farmers, physicians, root cutters, and other groups, as well as to the inhabitants of various regions (especially Macedonia, Arcadia, and the vicinity of Mt. Ida). His anonymous sources undoubtedly include not only oral reports but also technical writings, such as those by Diocles of Carystus on roots and poisons, and nontechnical writings, such as those by men who accompanied Alexander and noted vegetation of military importance or special interest along the way. (On the last see, for example, Historia, bk. IV.)

In his typological procedure Theophrastus makes no fundamental innovations; Aristotle had already used the same procedure in many other subjects, including zoology. Nor does he differ from Aristotle in his physiological theory. He regards plants as living things with a life dependent on the proportion of their innate heat and moisture and on the harmonious relation between them and their environment (Historia, I, 1, 1;2, 4f.; 11, 1; De causis, I, 4,6; 10,5; 21, 3; 22,2–3). His chief difference is, rather, in perspective. Aristotle regards plants as the lowest members of a system that culminates in man, as sharing with animals the nutritive faculty of the soul, and as illustrating similarities and dissimilarities within the system as a whole. Theophrastus, on the other hand, concentrates on the plants themselves and avoids systematization beyond his immediate subject. He does not speck of the plant’s soul; and, although he does use analogy between plants and animals, he emphasizes its limits and says that to strive after comparison where none is possible is a waste of effort and may cause us to abandon the method that is appropriate to the investigation (Historia, I, 1,4–5).

Theophrastus’ insistence on appropriate method follows from his recognition of the differences between plants and animals (Historia, 1,3,4) and of the manifold nature of plants. Generalization about plants as a whole is difficult because no part is common to them all as the mouth and stomach are common to all animals; they do not all have root, stem, branch, twig, leaf, flower, fruit, bark, core, fibers, and veins, although these and such parts belong to the plant’s essential nature (Historia, I, 1,10 f.). This diversity also makes it difficult to generalize about major classes and even about individual kinds; there is overlapping between classes, some plants seem to depart from their essential nature when they are cultivated (Historia, I, 3, 2), and each kind embraces several different forms (Historia, I, 14, 3). It is now clear why in the Metaphysics Theophrastus speaks of a method appropriate to plants as distinct from inanimate substances and even animals. In the study of such diverse material our object is not the universal but the particular, and our instrument is not reason but sense perception (De causis. II, 4, 8); we must pursue the unknown through what is manifest to the senses (Historia, I, 2, 3); and in offering explanations we must use causal principles that are in accord with the particular natures of the plants, for our accounts must agree with our observations (De causis, I, 1,1).

Consistent with this methodological principle, Theophrastus treats received theory and opinion with respect and skepticism, and seldom commits himself outright on one side or the other. Thus he quotes Aristotle’s dictum that nature does nothing in vain, but he does so only in support of what is already evident to perception (De causis, I,1,1). He explains the pericarp by anthropocentric teleology as being for man’s nourishment, but he goes on to explain it in relation to the seed (De causis, I, 16, 1; compare I, 21, 1). The reported infertility of cypress seeds makes him doubt that Aristotle’s dictum is true, but he does not renounce it (De causis, IV, 4, 2). So, too, Theophrastus speaks of spontaneous generation and transmutation as if they were simple facts; but again he offers explanations that might have led him to reject these notions, and in the end he leaves the question open (Historia, III, 1, 4–6; VIII, 8, 3–4). The same noncommittal attitude is evident in his treatment of particular reports. Along with the credible, he includes nonsensical tales, such as that the scorpion is killed by the application of wolfsbane but revived by white hellebore. His comment on this last is significant for his use of all the theories and evidence received from other: “Fabulous tales are not made up without reason” (Historia, IX, 18, 2).

By assembling his data impartially, classifying and discussing them within an elastic system, and withholding judgment when it was not secured by facts, Theophrastus created what he called an appropriate method and laid the groundwork for modern botany. Many of his observations and explanations were necessarily incomplete or erroneous; use of the simplest magnifying lens would have resolved many of his doubts. Among his contributions of lasting interest, his accounts of the following may be mentioned: the “pericarpion,” used for the first time as a technical term (Historia, I, 2,1); parenchymatous and prosenchymatous tissues (Historia, I, 2,5, f.); petalous and apetalous flowers (Historia, I, 13, 1); hypogynous, perigynous, and epigynous insertions of the corolla (Historia, I, 13, 3); centripetal and centrifugal inflorescences (Historia, VII, 2, 1–4).angiosperms and gymnosperms (Historia, I,11,2); monocotyledons and dictyledons (Historia, VIII, 2,1–4);. All except the firs of these terms are modern, but there is no doubt that Theophrastus correctly distinguished the features to which they are applied. In the last passage he gives the clearest and most accurate description of germinating seeds before Malpighi in the seventeenth century.

Theophrastus’ achievement in botany is all the more remarkable when we bear in mind that these two works were a small part of his writings. Their preservation does not allow us to suppose that botany was his primary interest; the loss of his works on other subjects may have been due not to their lesser importance but to the chances of manuscript transmission or to the tastes of later antiquity. Nothing in his writing indicates that he thought himself to be–as he has since been called–a professional botanist or that he considered his work comprehensive in detail or in theory. Of the plants that Theophrastus mentions only a third are not attested from other sources, and domesticated and familiar wild varieties are predominant (he says that most of the wild are nameless and little-known; Historia, I, 14, 4); he also omits many plants that he must have known.

Although some of his accounts (such as that of germinating seeds) indicate personal observation, they do not warrant the belief that Theophrastus had an experimental garden or made extensive field trips in Greece, let alone abroad. Nor is there any reason to think that he had collaborators or trained informants either in the Greek part of the Mediterranean or with Alexander’s army; if he had, there could hardly be so many gaps and uncertainties in his information. Some of his secondhand information he could not test himself; but, even when he could easily have done so, in some cases he did not (see, for example, Historia, VII, 1, 3–5). It may be asked what Theophrastus” intention was in writing at such length about incomplete and unverified evidence. The answer is probably to be found in his frequent reminders to himself and his readers that there must be further investigation. He was aware tat what he wrote was merely the beginning, that more and better data were needed, and that his explanations might need revision. His hopes apparently came to nothing. Later Greek and Roman authors enlarged the stock of useful knowledge and Pliny compiled it, but scientific botany progressed no further until the Renaissance.

Theophrastus was no less influential as a historian and critic of science than as a scientist. Besides several studies of individual pre-Socratics, he wrote a general history in sixteen or eighteen books known as the Physicorum opiniones. As Diels has shown this work was the direct or indirect source of many of the summaries made by the doxographers. The most extensive of these summaries, a handbook known as Placita philosophorum, was compiled by Aëtius in the second century from an earlier Stoic summary that in turn was based on Theophrastus’ history, with additions of later Stoic and Epicurean material. Through these and related summaries Theophrastus provided not only many of the details of pre-Aristotelian theories but also their selection and schematic arrangement.

It has been supposed that Theophrastus’ aim was to write an objective history, but this supposition may be questioned. The extracts on material causes that have been preserved from the first book, although they indicate firsthand knowledge of the pre-Socratic texts, closely follow the summary of causal theories given by Aristotle in Metaphysics I; and on other topics there are many similarities between the doxographers and the summary accounts of Aristotle. It would seem that the Physicorum opiniones was a compilation of Aristotle’s accounts, supplemented by quotations, biographical data, and other information omitted by Aristotle, and arranged under the main topics discussed by Aristotle. Aristotle’ purpost in discussing earlier theories is to put them in relation to his own–that is, to show to what extent they anticipated or approximated his and where they were inadequate; hence he reports only what is relevant to his theory and states it in terms of his theory. It may be that Theophrastus intended no more, that his history was a handbook to be used as background for his own exposition of Peripatetic theories. The use to which he might put such a handbook is suggested by his De sensibus, in which he reviews and criticizes earlier physiological psychology. Throughout he bases his criticism on Aristotle’s doctrine that sense perception involves qualitative change; and, even when he cites the texts of the writers whom he discusses (such as Plato’s Timaeus), he reformulates the theories so that they may be judged by Peripatetic standards.


I. Original Works, Editions of Theophrastus’ writings are J. G. Schneider, 5 vols. (Leipzig, 1818–1821); F. Wimmer, 3 vols. (Leipzig, 1854–1862), also one vol. with Latin trans. (Paris, 1866); and H. Diels, De sensibus and fragments of Physicorum opiniones, in Doxographi Graeci (Berlin, 1879).

Editions with commentary and translation are Historia plantarum (with De odoribus and De signis tempestatum), A. Hort, ed., 2 vols. (London, 1916); De causis plantarum, bk, I, R. E. Dengler, ed. (Ph. D. diss., Univ. of Pa., 1927); De sensibus, G. M. Stratton, ed. (New York, 1927); Metaphysics, W. D. Ross and F. H. Fobes, eds. (Oxford, 1929); De lapidibus, E. R. Caley and J. C. Richards, eds. (Columbus, Ohio, 1956), and D. E. Eichholz. ed. (Oxford, 1965); and De igne, V. Coutant, ed. (Assen, Netherlands, 1971).

II. Secondary Literature. See O. Regenbogen. “Theophrastos von Eresos,” in Pauly-Wissowa, Real-Encyclopädie der classischen Altertumswissenschaft, supp. VII, 1353–1562. Studies that have appeared since Regenbogen’s survey include. J. B. McDiarmid, “Theophrastus on the Presocratic Causes,” in Harvard studies in Classical Philogy. 61 (1953), 85–156, and P. Steinmetz, Die Physik des Theophrast (Bad Homburg, 1964).

J. B. McDiarmid

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