Source Verification: Apollo

Every claim below is either what a named ancient source attests, in its own line or section, or a point where the sources themselves disagree.

What the Sources Attest

What is Apollo the god of?

Homer and Hesiod present Apollo as presiding over several domains at once: prophecy and the Delphic oracle, music and the lyre, archery, and healing. His arrows could also send plague. In the Iliad, Book 1, he inflicts plague on the Achaean camp with those same arrows after Agamemnon insults his priest. His later identification with Helios, the sun, is not found in either Homer or Hesiod.

Source: Homer, Iliad, Book 1

When did Apollo become identified with the sun?

In the fifth century BCE at the earliest, and fully only among later philosophers. Homer's Odyssey still gives the sun its own god, Helios, who complains to Zeus when Odysseus's crew eat his cattle. The earliest clear equation is a fragment of Euripides's lost Phaethon, where the boy's mother calls the sun Apollo, the destroyer, punning on his name. The Stoics made it theology. Cicero's Stoic speaker says Apollo is called Sol, the sun, and Macrobius, around 400 CE, argues at length that Apollo and the sun are one god. Horace's hymn for the Secular Games still greets Sol and Apollo separately.

Source: Homer, Odyssey 12.374-388; Cicero, De Natura Deorum 2.68; Macrobius, Saturnalia 1.17

Where Accounts Differ

Python/Delphyne naming
twin birth order
solar identification

Serpent at Delphi: the Homeric Hymn to Apollo has Apollo kill an unnamed female serpent, later tradition calling her Delphyne, who guards a spring near Delphi; Apollodorus names the serpent Python and makes it the guardian of the oracle itself; Hyginus gives Python the further motive of having hunted the pregnant Leto at Hera's order.
Birth order of the twins: the Homeric Hymn to Apollo gives no birth order for Apollo and Artemis. Apollodorus's Bibliotheca adds that Artemis was born first and served as midwife for Apollo's birth, because Hera had detained Eileithyia, goddess of childbirth.
Solar identification: Homer and Hesiod keep Apollo distinct from Helios, the sun-Titan who drives the sun's chariot. Apollo's identification with the sun is a later development in antiquity and is not attested in either source.
The earliest clear equation of Apollo with the sun is a pun in a fragment of Euripides's lost Phaethon. Cicero reports it as the Stoic view (De Natura Deorum 2.68), and Macrobius argues for it at length (Saturnalia 1.17). Horace's Carmen Saeculare still addresses Sol and Apollo in separate stanzas.

Sources

Primary sources

Homeric Hymn to Apollo 1-178
Hesiod, Theogony
Homer, Iliad 1.43-52
Apollodorus, Library
Hyginus, Fabulae
Ovid, Metamorphoses
Aeschylus, Agamemnon 1195-1215
Ovid, Metamorphoses 11.146-193
Apollodorus, Library 1.6.2
Apollodorus, Epitome 5.18
Virgil, Aeneid 11.768-793
Virgil, Aeneid 11.794-835
Apollodorus, Epitome 5.3
Homer, Odyssey 12.374-388
Euripides, Phaethon
Cicero, De Natura Deorum 2.68
Macrobius, Saturnalia 1.17