Scholia are grammatical, critical, or explanatory comments, either original or extracted from pre-existing commentaries, which are inserted on the margin of the manuscript of an ancient author, as glosses. One who writes scholia is a scholiast. The earliest attested use of the word dates to the 1st century BC.
History
Ancient scholia are important sources of information about many aspects of the ancient world, especially ancient literary history. The earliest scholia, usually anonymous, date to the 5th or 4th century BC. The practice of compiling scholia continued to late Byzantine times, outstanding examples being Archbishop Eustathius' massive commentaries to Homer in the 12th century and the scholia recentiora of Thomas Magister and Demetrius Triclinius in the 14th. Scholia were altered by successive copyists and owners of the manuscript, and in some cases, increased to such an extent that there was no longer room for them in the margin, and it became necessary to make them into a separate work. At first, they were taken from one commentary only, subsequently from several. This is indicated by the repetition of the lemma, or by the use of such phrases as "or thus", "alternatively", "according to some", to introduce different explanations, or by the explicit quotation of different sources.
Some ancient scholia are of sufficient quality and importance to be labelled "commentaries" instead. The existence of a commercial translation is often used to distinguish between "scholia" and "commentaries". The following is a chronological list of ancient commentaries written defined as those for which commercial translations have been made:
Asconius on Cicero's Pro Scauro, In Pisonem, Pro Milone, Pro Cornelio and In Toga Candida
Servius on Virgil's Aeneid
Macrobius on Cicero's Dream of Scipio
Proclus on Plato's Parmenides and Timaeus and Euclid's Elements
Boethius on Cicero's Topics
Other uses
Spinoza provided his own scholia to many of the propositions in his Ethics, commentaries upon and expansions of the individual propositions, or sometimes short conclusions to sections of argumentation running over a number of propositions.
In modern mathematics texts, scholia are marginal notes which may amplify a line of reasoning or compare it with proofs given earlier. A famous example is Bayes' scholium, in which he presents a justification for assuming a continuous uniform distribution for the prior of the parameter of a Bernoulli process. Another famous example of a somewhat different use is to be found in Brook Taylor's Methodus Incrementorum, in which the propositions demonstrated are often followed by a scholium which further explains the significance of the proposition.
Nicolás Gómez Dávila was one of the most radical critics of modernity whose work consists almost entirely of aphorisms which he called "escolios" of an implicit text.
