My research on Thucydides highlighted the wide range of documents that the historian used: treaties, inscriptions, letters, laws and decrees, oracular responses, literary works, oaths, arbitrations, charters for the foundation of colonies, and lists of various kinds.

I have been able to identify 34 decrees in total, of which 19 are Athenian and three Spartan; the rest were approved by several political communities, by the Athenian or by the Peloponnesian League, for example, and even by members of illegal governments, such as the Thirty Tyrants or the Three Thousand. The terminology used by Xenophon privileges, instead of nouns of juridical nature, their corresponding verbs: ψήφισμα (6), δόγμα (3), γνώμη (2), but more often ψηφίζομαι and compounds (16), δοκέω and compounds (10), δίδωμι (1), and also expressions such as ψῆφον φέρειν (1) and ψῆφον δίδωμι (1).

Particularly interesting is Xenophon’s reference to Aristotle’s Decree and to the δόγματα of the allies (ψηφίσματα) in the text of the oath sworn for the Peace of Athens in 371/0 mentioned above:

It is noteworthy that Xenophon refers to Aristotle’s Decree (whose text was available in the corresponding inscription) in this passage only, only hinting at it by way of another document.

But Xenophon’s interest in epistolary documents is equally clear in later books of the Hellenica, where he mentions letters of the Persian King, including the clauses of the King’s Peace and of the Peace of Susa. These two documents have already been discussed with regard to the corresponding peace treaties: here it should only be recalled that Xenophon fully transcribes the text of the first letter (5.1.30–31; he also alludes to it at 5.1.32 and at 6.5.2) while only referring to the second (7.1.39–40); in both cases, he stresses that the letter is read out and that it bears the royal seal in order to establish the authenticity of the document:

Thus, just as with Thucydides, so too with Xenophon may we speak of the notable ‘documentary’ prestige of the letter, even though in the latter the range of documentary material is less wide. It is worth noting that the three letters of the Persian King are the sole documents whose authenticity is emphasized, although this may be a result of historical (rather than strictly historiographical) factors; that is to say, it is not (primarily) Xenophon who wants to assure his public that he is referring to authentic documents, but the King who wants to prove the authenticity of his message to the Greeks. {102|103}

Xenophon mentions an oracle by Olympian Zeus for Agesipolis at 4.7.2. The response was uttered in the spring of 388 on the occasion of a military expedition against Argos; in the following paragraph the historian recalls the oracle of Delphic Apollo on the same issue, which he paraphrases as follows:

With regards to content, Thucydides and Xenophon are essentially interested in the same types of documents. Most of the documents cited have political relevance and refer to international relations; legal and religious documents are also well represented. Documents with administrative and economic interest, however, seem to be less relevant: we may recall in the former category the suspect list of the Thirty and the list of the ephors, probably interpolated; in the latter, the decree mentioned at 5.2.10, by which property was restored to those exiled from Phlius.

Xenophon’s preferred methods of citation are references and paraphrase, although it is sometimes difficult to distinguish between the two (the use of technical, formulaic expressions speaks in favor of the latter). We find few cases of full or partial transcription, about half the number in Thucydides.

The five cases of full transcription are the letter of the Spartan Hippocrates intercepted by the Athenians in 411 (1.1.23), which is introduced by λέγοντα τάδε; the γνώμη of Kallixenos (1.7.9–10) introduced by εἰπόντος τήνδε (γνώμην); the list of the Thirty Tyrants (2.3.2), introduced by καὶ ᾑρέθησαν οἵδε; the text of the King’s Peace (5.1.30–31), introduced by εἶχε δὲ ὧδε; and the oath of the Peace of Athens of 371/0 (6.5.1–3), introduced by τόνδε τὸν ὅρκον. To these documents we should add the (probably interpolated) list of the ephors mentioned above. {107|108}

On the whole, we may conclude that Xenophon is less interested than Thucydides in transcribing documents: yet the documents he does transcribe {108|109} are often very important for our historical knowledge, such as the γνώμη of Kallixenos, the list of the Thirty Tyrants (if it is not interpolated), the text of the King’s Peace, and the oath of the Peace of Athens of 371/0.

There are several reasons why Xenophon might have transcribed a document: his wish to clarify political or military events (the letter of Hippocrates) or trials (the γνώμη of Kallixenos) by citing documents that support his interpretation; his intention to furnish complete evidence (the list of the Thirty); his wish to emphasize the relevance of the κοινὴ εἰρήνη as a fundamental principle in fourth-century international law (the texts, fully or partially transcribed, of the common peaces); and, last, his interest in international relations, which also explains why treaties are the best attested type of document in the Hellenica.

Thucydides never states the origin of his information unless he cites a literary work (e.g. Homer and the ancient poets) or refers to inscriptions. In Xenophon, who cites neither epigraphical documents nor literary works in his Hellenica, such information about sources is almost completely lacking. There are cases of documents cited in speeches, however, such as the two decrees (of the Peloponnesian League and of the Thebans) mentioned by the Theban ambassadors who came to Athens in 395 (2.2.15) and the Olynthian decree on the alliance between Athens and Boeotia, recalled by Cleigenes of Acanthus in the Spartan speech of 382 (5.2.15). The word λέγεται, which introduces Xenophon’s reference to the Delphic oracle about Jason of Pherae (6.4.30), also seems to refer to an oral tradition. Sometimes (especially in the case of lists, letters, treaties) the use of the verb γράφω, γράφομαι, and their compounds may imply the availability, even through a public reading, of a written document; in fact, a public reading is expressly mentioned with reference to the clauses of common peace treaties (cf. 5.1.30 for the King’s Peace and 7.1.39 for the Peace of Susa). However, we can never exclude the mediation of eyewitnesses (Agesilaus or other Spartans; Athenian ambassadors).

In Thucydides the physical location of documents is implicitly clear only for inscriptions and literary works. For other types of documents, except where the historian does provide explicit information, it is very difficult to form an opinion. In Xenophon, who never refers either to inscriptions or to literary works, information on the location of documents is lacking: we may only suppose that some documents come from archives (for example, in the case of the documentary material regarding the Arginousai trial).

As I emphasized in my paper from 2003, Thucydides is specifically interested in “documents”, which he uses for historiographical and not merely decorative purposes. This historiographical interest is essentially confirmed in Xenophon, although the range of documents he considers is less broad than that of his predecessors, and he seems less inclined to transcribe documentary texts.

The prominence of international treaties and decrees, i.e. documents with political value, corresponds to the historiographical nature of the Hellenica; the treatment of other types of documents leads to the same conclusions (oaths mostly regard the undersigning of international treaties or civic agreements; all letters have an indisputable political value).

Finally, the scanty interest in oracles shown by the ‘pious’ Xenophon is remarkable: Thucydides, who is not usually considered to have been particularly interested in religious matters, pays much more attention to oracular responses.