PERIPATETIC, SCHOOL OF. — The followers of Aristotle were called οἱ ἐκ τοῦ περιπάτου in reference to the walkway (περίπατος) of the Lyceum (the school’s seat), and περίπατητοι (a word connected with περίπατος) in reference to their custom (common to other schools as well) of disputing while walking. This, at least, still seems the most plausible solution to the well-known etymological question that has arisen around the name.
In the history of the school itself (which was also simply called “Peripato”) several periods must be distinguished. Among the Peripatetics of the first generation after Aristotle’s death, the principal figures were Theophrastus of Eresus (v.), Eudemus of Rhodes (second half of the 4th century B.C.), Dicaearchus of Messina (a versatile writer whose acme can be placed around 310 at the latest), Aristoxenus of Tarentum (born between 375-60, a distinguished theorist of music), Clearchus of Soli, and Demetrius of Phalerum (born ca. 350 B.C.), a pupil of Theophrastus. The orientation they gave to the school is characterized by extensive research in natural science, literary history, and various erudition, as well as by treatments of popular ethics, to the detriment of metaphysics. Of the Peripatetic production of this period, there remain Theophrastus’ *Characters*, two botanical writings and some other scientific treatises by Theophrastus himself, Aristoxenus’ *Elements of Harmony* (*Ἀρμονικὰ στοιχεῖα*), a portion of his *Elements of Rhythm* (*Ῥυθμικὰ στοιχεῖα*), and only fragments of other works. Among the lost philosophical writings are Dicaearchus’ dialogues *Corythiacus* and *Asbyticus*, in which the Messinian denied the substantiality of the soul. This same direction of the Peripatetic school is maintained, indeed accentuated, in the first part of the Hellenistic age. The Aristotelians continued to devote themselves actively to the natural sciences and to the various fields of history. In philosophy, the most notable figure is that of Strato of Lampsacus, the “physicist,” successor of Theophrastus in the headship of the school (which he held from 288-87 [or 287-86] until his death in 270-69 [or 269-68]). Strato distorted Aristotle’s doctrine in a distinctly naturalistic sense, identifying God with natural necessity and approaching the thought of Democritus (v.). A pupil of Strato was Aristarchus of Samos (d. after 264 B.C.), the astronomer who anticipated the Copernican heliocentric conception. Other Peripatetics of this period were Lyco of Troas (ca. 300-225 B.C.), scholarch for many years, Ariston of Ceos (3rd century B.C.), Critolaus of Phaselis (first half of the 2nd century B.C.), Diodorus of Tyre (flourished in the first decades of the second half of the 2nd century B.C.). In literary and philosophical history, there were Eratippus (3rd century B.C.), Sotion (author of a *Diēs dystychiai*, a work on the fortunes of philosophers, between 200 and 170 B.C.), Satyrus (3rd century B.C.), Heraclides Lembus (2nd century B.C.), and others. Many of the notices we have about Greek authors of the classical age ultimately derive from the works of these men; and to the Peripatetics is also owed the formation of that particular literary genre which is biography. The Peripatetic school, however, as an institution, suffered a decline from the time of Lyco, from which it was not to recover until the age of Andronicus.
In the 1st century B.C., precisely a third phase begins, and a renewed splendor of the school itself. A fruitful and imposing scholarly labor was devoted to the works of the Stagirite, which Andronicus of Rhodes (v. flourished ca. 70 B.C), the tenth or eleventh in the order of the scholarchs, collected, arranged, published in a new edition, and commented upon. The imperial age is marked by a notable series of commentators on Aristotle, among whom Alexander of Aphrodisias (v. 2nd century A.D) excelled, the so-called “second Aristotle,” whose exegeses were to have a very strong influence even in the Middle Ages. Important studies on Aristotle were also devoted by Boethus of Sidon (perhaps living in the Augustan age), author of a commentary on the *Categories*, Ariston of Alexandria (first half of the 1st century A.D.), also a commentator on the *Categories*, Seneca of Seleucia (Augustan age), and the polygraph Nicomachus of Damascus (born ca. 64 B.C.; teacher of Nero), Alexander of Aegae (1st century A.D.), Ptolemy Chennus (philosopher and grammarian flourishing ca. 100 A.D., author of a work on the life and writings of the Stagirite), Aspasius (first half of the 2nd century A.D.), Adrastus of Aphrodisias (ca. second half of the 2nd century A.D.), Herminus (2nd century A.D.). It is worth noting that in this age there is a revival of interest in Aristotle’s metaphysics and logic, to which the Hellenistic Peripatetics had devoted little attention. And it is precisely at this time that Aristotelianism is given that configuration as an organic system with which it would be handed down to the Middle Ages. Meanwhile, while the Peripatetic school in general remained fairly orthodox and conservative with respect to the master’s thought, there were also representatives of an eclectic Aristotelianism, such as the author of the pseudo-Aristotelian *Elenchos* (in which an attempt is made to reconcile Aristotle with Stoicism); the famous geographer and astronomer Claudius Ptolemy (2nd century A.D.); Galen (v.).
One of the last ancient Peripatetics is Themistius (v.), author of *Paraphrases* of various writings of the Stagirite.
When the Sacred Roman Rota extended its jurisdiction to civil cases as well, it made use of arbiters in pecuniary matters; their decision was also the decision of the case, and the dispute was thus considered settled. In time, the arbiters became rather “qualified experts” elected by the judge to enlighten him on a particular matter or art in which they were specialized. Thus the experts became true “assistants” to the judge, by whom they were elected and to whom they were accountable; at the same time, they were quite distinct from witnesses and far superior to them, precisely because they were chosen with the aim of examining the fact asserted by the witness, then reporting to the judge, issuing, for the technical side of the question, a true monitory judgment. Thus, through the evolution of the Sacred Roman Rota, the present-day figure of the expert has come into being, which, though not well defined, is accepted in almost all modern codes.
In the *Codex Iuris Canonici* this is required only when no other kind of proof is available. Expert testimony is considered an extraordinary means, also because it is generally quite costly. The expert is prescribed, *ex officio*, in important matrimonial cases of impotence (can. 1976) or insanity (can. 1982), and in beatification causes for the examination of miracles (can. 2031; V. BEATIFICATION, vol. II, cols. 1094-95). In many other matters, such as, for example, to examine the authenticity of a writing (can. 1800), in controversies over *novi operis nuntiatio*, in those concerning the boundaries of ecclesiastical circumscriptions, in criminal cases, for forgery or theft of precious objects, the judge himself may deem the expert’s work necessary, just as the expert may be requested by one or both of the parties. The appointment, however, always belongs to the judge, who will consult, according to the case, with the defender of the bond or with the promoter of justice. In civil trials, on the other hand, the parties are allowed to elect the expert, who acts in their interest. In certain causes the *Codex* prescribes two experts (cf. cans. 1979, 2031, and 2118); in others, a single expert may be appointed (cf. can. 1793 § 3), according to the judge’s prudent discretion. When it is found that the matter has not been sufficiently clarified, the judge may appoint a second and a third expert. If, then, the conclusions of two different experts who have acted independently of each other are discordant, the judge may appoint a referee, who, after examining all previous acts, will give a new judgment (cf. can. 1803 § 1).
The judge shall choose the expert from among persons competent in a particular profession or art and absolutely worthy of esteem. The name of the expert shall be immediately notified to the interested parties, to allow them to raise any objections. It is always for the judge to declare, by decree, whether it is appropriate to revoke the mandate of the expert or not and to appoint another (can. 1796). The interested parties may attend the expert’s oath and be present while he performs his mandate, unless propriety, modesty, or another consideration forbids it (can. 1797).
The expert shall take an oath, both at the moment when he is about to accept the mandate (iuramentum de munere fideliter implendo); sometimes the oath de secreto servando is added. The expert may present his reasoned report in writing, or exceptionally orally; in the latter case, however, the report must be immediately recorded in writing and signed by the expert and the notary (can. 1801 § 1). After the expert has contested the written report, he is summoned to the tribunal to confirm it in writing or by oath and, if necessary, to provide further clarification.
When two experts are appointed simultaneously for a matter, they normally act independently of one another, and each must draw up his own report. An exception to this practice may be made in cases of a process for relative impotence, where a medical examination of the man and the woman is necessary.
In such cases, one expert examines the man and the other the woman, according to their respective specializations; then they consult together to compare their findings and draft the expert report. If the two opinions are not in agreement, this may be noted in the drafting of the report without specifying which expert holds which opinion. The conclusions of the expert are of great value for the judgment; however, by the principle of the judge’s free assessment of evidence, the judge is not bound by the expert’s conclusions, and his sentence is entirely original and autonomous, especially since for the definitive decision he must consider the entire complex of circumstances, sometimes unknown to the expert. Every expert report shall remain on the record as part of the proceedings; in exceptional cases, it may not be admitted or may be annulled.
It is not uncommon for an expert to draw up a written report not under formal mandate from the judge but merely at the request of an interested party or a legal representative. Such an initiative, generally taken at the beginning of a process, aims to present the case in a favorable light, making it appear to have a valid foundation rather than merely a *fumus boni iuris*. In such a case, the report is called *extrajudicial* and may be regarded as a technical defense. The expert in these cases assumes the true role of a witness and, as such, is summoned to the tribunal to acknowledge his report.
Particular instructions for expert reports, both in cases of unconsummated marriage and in those of nullity, are found in two documents issued by the Sacred Congregation of the Sacraments: *Regulae servandae in processibus super matrimonio rato et non consummato* of 7 May 1923, arts. 84–95; and *Instructio servanda a tribunaliis dioecesanis in pertractandis causis de nullitate matrimonii* of 15 August 1936, arts. 139–54.
On 12 June 1942, the Supreme Sacred Congregation of the Holy Office issued a decree *De quibusdam cautelis adhibendis in causis matrimonialibus impotentiae et inconsummationis*, by which it renews the advice to have women examined by female doctors, and only upon explicit request by male expert doctors. Moreover, no woman may be compelled to undergo a medical examination, even when an expert report might appear strictly necessary for the resolution of the case.