Cobet’s family moved from France to Holland, where he passed through the gymnasium at The Hague and was inscribed in the Faculty of Theology of Leiden University (1832). Being one of the few visitors of the university library, Cobet spent many days perusing Greek and Latin texts, and he became an intimate friend of the librarian Johan Jacob Geel, who guided his interests in a most beneficial way. Two years later Cobet switched over to classical philology and at about the same time (December 1835) he won the gold medal of the Faculty by writing a Prosopographia Xenophontea.This masterpiece resulted in his being welcomed gladly by the Leiden philologists Janus Bake (1787-1864) and Petrus Hofman-Peerlkamp (1786-1865). In order to finish his studies a testimonial for hearing historia iuris by Johan Rudolf Thorbecke (1798-1872)—in later years a famous Dutch statesman—was indispensible, but Cobet could not see the relevance of this subsidiary specialism and he was not inclined to meet this obligation; by this unusual behavior Cobet’s independent and willful character made itself manifest at an early stage. The result was a deadlock, all the more serious because the Royal Institute wanted to patronize a new Simplicius edition and was prepared to send the young scholar to France and Italy in order to make the appropriate collations of manuscripts. Fortunately, Bake found an excellent way out by making Cobet defend an unauthorized but full-sized thesis (on 20 October 1840) that enabled Bake to confer the degree doctor honoris causa on Cobet some months later, on 17 March 1841.
At that time Cobet was already in Paris, where he had to discover for himself that the Aldina of the Commentarii De caelo was indeed a late Greek translation of the thirteenth-century Latin version by Willem van Moerbeke. He stayed abroad for five years exploring the libraries of Paris, Turin, Florence, Rome, Naples, Milan, and Venice, not only collating a total of some eighty-five Simplicius manuscripts, but all taking a keen interest in all other texts he came across, recording important variae lectiones, with a clear preference for Attic prose and Homeric scholia (on finding the codex Venetus B, Cobet immediately recognized its importance). As the government only paid for three years, Cobet accepted an invitation from Firmin Didot to provide a new edition of Diogenes Laertius, a task he finished with great reluctance, as he thought it absurd to add a Latin translation. However, the edition was published at last in 1850 without a foreword and it remained the leading one for more than a century. As the correspondence with his friend Geel was carefully preserved by the addressee, we are in the happy position of being able to follow Cobet week by week from November 1840 to July 1845 in his quest for manuscripts while he unremittingly ransacked French and Italian libraries and copied thousands of text variants; these letters, giving information and comments upon many difficult passages, betray both a youthful energy and enthusiasm, and a vehement, often improper criticism of librarians and other scholars.
After his return, Cobet in 1846 became Extraordinary Professor of Rome Antiquities at Leiden (succeeding W. L. Mahne (1772-1852), the insignificant panegyrist of Wyttenbach), but he soon rose to the chair of Hofman Peerlkamp(1786-1865), being entrusted with the teaching of Greek in accordance with an arrangement with Bake, who took charge of the Latin department. Cobet remained in function for more than thirty-five years, though in the end he suffered from apoplectic fits that impaired his memory and ultimately proved fatal.
Cobet was mainly concerned with textual criticism, and nearly all his publications, varying from his thesis through Commentationes philologicae (1853), Variae and Novae Lectiones (1854; 1859) to Miscellanea and Collectanea critica(1876; 1878), contain numerous emendations to and conjectures on the whole range of Greek prose literature (cf. the useful inventories in Mnemosyne n.s. 34  430-448; 35  440-449).
In his very instructive inaugural Oratio de arte interpretandi grammatices et critices fundamentis innixa primario philologici officio (1847), Cobet laid down the leading principles of his approach to Greek language and literature. These lines were further defined in his yearly adhortationes or allocutiones with which he began his lectures in order to encourage the students; some of these were published in 1852, 1853, 1854, 1856, and 1860. He honestly believed that the Greeks, and first and foremost the Athenians, were able, as long as they enjoyed freedom, to express in their Attic language a supreme rationality and lucidity in combination with a natural elegance and feeling for nuance. While learning the grammatical subtleties of pure Attic it should, however, be observed that each author had his own peculiar way of thinking and relating; students should be reminded that reading Greek meant listening to a human being with his own idiom and style. Consequently, lexica abicere et si sufficere mature docendus est quicumque iustam certamque antiquae linguae scientiam quaerit, as dictionaries usually mixed up forms and meanings from different authors and different periods. It was only during the classic period that Greek usage was consistent and precisely defined. With the arrival of Alexander the Great, Greece was deprived of its independence, Attic speech lost its natural purity and spontaneity, and it became ever more liable to degeneration and corruption. The post-Alexandrian authors, though still emulating the classical examples and writing an even more elegant Attic, were too much influenced by words and expressions borrowed from non-Attic dialects and from vulgar speech.
The normative power of Attic was mainly due to its grammatical perspicuity, the constancy in the meaning of words, and the clear structure of sentences; its grammar was ruled by the laws of analogy, and these guaranteed an ideal precision and adequacy of expression. A full knowledge of Greek might ultimately lead one to reach the highest grade of humanitas.
In these views Cobet proved himself to be a true representative of the early nineteenth-century trend of classicism. He had assimilated his mind so completely to Greek thinking that he confessed he usually read Latin by translating it into Greek. This mentality led him to a way of handling old manuscripts—always intent on making corrections in order to eliminate the grammatical faults and misinterpretations of medieval copyists—that was appreciated neither by many contemporary German colleagues nor by most of his modem Dutch successors. His hypercorrective attitude toward traditional readings made him neglect many peculiarities nowadays recognized as true and original Attic forms or phrases. So he would not accept the feminine dual forms τά, ταῖν, etc., and corrected them to τώ, τοῖν, etc., though these forms are doubtless good Attic (cf. G. L. Cooper III in TAPA 103 (1972) 97-125, who showed that some feminine forms seem to have a hypocoristic connotation about them). Other typical Cobetian corrections were: 1) changing forms of the present (e.g., imperfect) into aorist, 2) changing imperfect to pluperfect, 3) inserting optativi obliqui instead of indicative forms, 4) preferring future infinitive or aorist infinitive + ἄν to aorist infinitive, 5) deleting verba dicendi in oratio obliqua.
In recent years Cobet’s “critical philosophy” has been severely criticized by E. J. Kenney (The Classical Text,Berkeley and Los Angeles, 1974:117-123), who rightly observes that Cobet did not avail himself of the innovative methods of recensio as espoused by his contemporaries Madvig and Lachmann, and in his Observationes criticae et palaeographicae in Dionysii Halicamassensis Antiquitates Romanas (Leiden, 1877) ignored Ritschl’s stemma codicum.Cobet stubbornly kept to the doctrine of restoring the text sive ex antiquis membranis sive ex ingenio sanctified by his illustrious predecessors Ruhnken and Scaliger. Nonetheless, it cannot be denied that Cobet gave an indisputable proof of his skill as a textual critic by collating and classifying the manuscripts of Simplicius’ Commentarii; he indeed identified the Laurentianus 85.21 as the archetype of the Commentarii de anima and, as Sicking rightly noticed (1984), Cobet’s method of differentiating between good and bad manuscripts does not actually depart from the rules laid down by M. L. West (Textual Criticism and Editorial Technique, Stuttgart, 1973: 37ff.) in the case of an open recension; in the same way, Cobet’s harsh and damning qualification of medieval monks and scribes as mendacious falsifiers can easily be paralleled with comments made by modern authors in this field.
Unfortunately, Cobet’s preliminary work on Simplicius’ Commentarii—at first a complete edition was planned by the Royal Dutch Academy—only resulted in the publication of the Commentarii de caelo by S. Karsten in 1865. As Cobet himself did not have any philosophical inclinations and referred to such speculations as λήροι λεπτότατοι, he concentrated all his acumen on the constitution and interpretation of Greek prose texts, especially the historical works of Herodotus, Thucydides, Xenophon, and the Attic orators like Demosthenes, Lysias, Antiphon, and Aeschines. He took a particular interest in Hellenistic scholarly literature (e.g. Athenaeus, Galen, Clement of Alexandria, Photius, Stobaeus, and Strabo), as it preserved countless quotations from lost drama or comedy. Having a quick and witty mind, Cobet found much pleasure in looking for comic fragments of Menander, and since many were stored by Athenaeus, he collated all the manuscripts in question on the basis of the Venetian archetype. Above all Cobet loved Homer—he thought him an Athenian!—and he did much to make his way of thinking better understood, e.g. by vindicating many ἀπρεπῆ in verses discredited by the bad taste of the Alexandrians. In drama, he contributed some good emendations to Sophocles and Euripides (i. e. Helen), though he frankly confessed that he did not feel at home in poetry, and the more so if he could not find an animi sanitatem et φρόνημα in it. Accordingly, he could not appreciate Callimachus because of his sophisticated erudition and artificial style, nor Theocritus, who confused old and new forms in an unpleasant way. When comparing the works of later prose writers with the rules set by the Atticistic grammarians, Cobet spent much time and energy in trying to distinguish faults caused by paleographic errors from those due to the grammatical carelessness of the prose writers themselves; while doing so he abominated the empty talk of Aelian and Longus, but he was very much pleased with Lucian’s veterum nitidam et tersam dictionem, cogitandi serenitatem, louendi sanitatem. Always looking for normative rules and clear expression he showed himself a real nineteenth-century Dutchman, who put zeker weten en helder inzicht(“definite knowledge and clear insight”) above all.
This narrow-minded but consistent attitude made him an extraordinary mainstay to all those students who loved him intensely and spread his learning and ideas. After 1864 nearly all Dutch university chairs of classical philology were successively occupied by pupils of Cobet: in Utrecht, Henrich Van Herwerden (1831-1910), J. Van der Vliet (1847-1902), and Johann Christoph Vollgraff (1848-1920); in Groningen, Tjalling Halbertsma (1829-94) and Hermann Joseph Polak(1844-1908); in Amsterdam, Samuel Adrianus Naber (1828-1913) and Jan Boissevain (1836-1904); in Leiden, Jan Jacob Cornelissen (1839-91), Jan Van Leeuwen (1850-1924), J.J. Hartman, and Dirk Christtiaan Hesseling (1859-1941). Willem Nikolaas Du Rieu (1829-96) and Scato Gocko de Vries (1861-1937) made their mark as Leiden librarians. Many distinguished schoolmasters and rectores gymnasii had been trained in conformity with Cobetian standards, and even the later famous Sanskritists Johan Hendrik Caspar Kern (1833-1917) and Willem Caland (1859-1932) owed their critical methods mainly to Cobet. This is all the more remarkable as Cobet had a dislike for comparative linguistics and severely criticized its lack of grammatical knowledge (λινγυιστικη!) and jeered at these συ/αγκριτισταί.
Neither the archaeological remains in Rome and Pompeii nor the works of art that Cobet saw in Florence and Naples left a strong impression on him; yet he was fully alive to new finds in papyrology and epigraphy and he took an active part in revising recently discovered texts or inscriptions. Thus, he prepared new editions of Hyperides’ ᾿ΥπὲρΕὐξενίππου, Λόγος ἐπιτάφιος (1877) and of Philostratus’ Περὶ γυμναστικῆς (1859), while his stay in Venice (1844) gave him the opportunity to study three Cretan inscriptions relating to Hierapytna (=Inscr. Cret. Ill, 3,3).
Greek and Roman antiquities had early aroused Cobet’s interest, as he was put in charge of teaching this particular subject. Accordingly, several chronological problems and the analysis of sources in Plutarch’s Lives I-XI (especially Pericles, Aristides, Themistocles, Alcibiades) were carefully studied as well as those in the writings of Duris of Samos and in Dionysius’ Roman Antiquities, the latter being gathered in Observationes in Dionysii Ηalicamassensis Antiquitates Romanas (1877). As to the Gracchi, Cobet tried, against Cicero, to justify their policy, while he did not shrink from caviling Mommsen.
This preferential treatment of historical authors, in combination with a resolute aiming at an improvement of Dutch educational practice, made Cobet prepare a clean Attic edition of Xenophon’s Anabasis and Hellenica that became standard reading in the gymnasia for nearly a hundred years. Though at the outset destined only for school practice, these texts gradually achieved a prescriptive status. In the same way Cobet lent his genius to two other schoolbooks: 1) a revision of the Nepos edition originally prepared by his colleague W. G. Pluygers and 2) a strange phenomenon in Dutch pedagogic tradition—a collection of nearly 500 jokes (asteia) taken from Philogelos and remodeled into a fashionable Greek. Some people were a little shocked at this publication, but many teachers were glad to have their lessons spiced by these funny stories.
After all, Cobet was both a creative scholar and a brilliant speaker, who knew how to inspire his pupils with a lasting confidence in the superiority of classical literature and who was always ready to encourage and help them. Not a few foreign scholars acknowledged their debt to Cobet, “the greatest Greek scholar of this century,” as W. G. Rutherford, the author of an exemplary Phrynichus edition, qualified him in the obituary in CR 3 (1889) 470-474. Yet the number of students attracted by Cobet from abroad was very limited; among these was the later Nestor of the Athenian faculty, Constantine Contos, who came to Leiden as a young man to improve his knowledge of Greek. Many scholars profited from the collations Cobet had made in Italy, and these were generously put at their disposal, like A. Emper (Dio Chrysostom), L. Kayser (Philostratus), W. Dindorf (Scholia Homerica), W. A. Hirschig (Erotici). In later years, Cobet’s extreme negligence of German literature and his failing memory raised many sharp polemics and blunt insinuations by colleagues who, like Gregorios N. Bernardakis (1848-1925) and Theodor Gomperz (1832-1912), thought they could prove the priority of other scholars in proposing conjectures. On glancing through the critical apparatus of some texts commented on by Cobet, it is not difficult to point to some emendations that can now justly be traced back to their originator, but at the same time it is curious to see other Cobetian corrections attributed to later distinguished scholars. Cobet would not worry about such questions; instead, he would probably have said: “nunc ad seriora transeamus,” as he used to say when in university examinations it was his turn to test the knowledge of the candidate in Greek after philosophy or archaeology had been examined.