Q: What did Sallustius mean when he wrote:
"Those who make the world are Zeus, Poseidon, and Hephaistos; those who
animate it are Demeter, Hera, and Artemis; those who harmonize it are
Apollo, Aphrodite, and Hermes; those who watch over it are Hestia,
Athena, and Ares."
This is a pretty standard later Platonic classification scheme, not as mysterious as it sounds, if a little complex. I'll try to explain what's going on, fleshing out Sallustius' abbreviated account with the much fuller account we get from Proclus.
Sallustius is classifying the Gods according to the disposition they adopt toward the world (cosmos). These are classifications of modes of activity. It is important to remember that these are only facets of the total activity of the Gods involved. The primary importance of these classifications is what they say about the structure of being, about the products of the Gods' activity; as determinations of the nature of the Gods they are necessarily limited, because there is always a surplus of existence over activity in divine individuals--they ARE always more than they DO.
Note that Sallustius is not discussing all the Hellenic Gods; he's discussing a select set of Gods from the intellective and hypercosmic (i.e., supervising-the-cosmos) classes.
Zeus, Poseidon, and Hephaistos are 'makers', dêmiourgoi. One must understand that it is never a question in Greek thought of creation from nothing, ex nihilo, but of giving order to a system. You can see how this works by reading Plato's Timaeus, where Plato, through the voice of the Pythagorean Timaeus of Locri, describes this cosmogonic process in general, abstract terms. Demiurgy there is a process of giving order to motion. It is also important to recognize that the 'making' in question here is not something that happened once and now is done. Everything the Gods do, they're doing now and they've always done; this is the Platonic perspective, at any rate. Therefore, this is an ongoing process of form-giving. (This is just like Egyptian theology, where the time of cosmogony is always now.)
Sallustius would have us recognize three different modes of formative activity in the trio of Zeus, Poseidon and Hephaistos. Zeus gives form to the realm of ideas, Poseidon to the realm of generation, Hephaistos to the realm of bodies. When we strive to understand formal structures, ideas and ideals, when we do, in effect, what philosophers do, we operate in Zeus' realm; when we engage with other living things in the flux of becoming, we are in the realm of Poseidon, on his 'seas'; the realm of physics, of chemistry, of corporeality as such, belongs to Hephaistos. These Gods are responsible for the order we discover in these realms--the laws of the concept, of the psyche, of physical nature, are in this sense acts of Zeus, of Poseidon, of Hephaistos, respectively, expressions of their natures, and these sciences are in some respects a path to them for us as well.
The lifegiving or vivific Gods (zoogonikoi theoi) are an order of intellective Gods imparting self-motion, because this is what is essential to the category of life in Greek thought--it is a question, you see, of elucidating the categories of Hellenic thought as the fingerprints, so to speak, of the activity of the Hellenic Gods, because all of Hellenic thought and culture is their revelation, their view of each other and hence of the nature of being rendered concrete, their cosmogenesis. Life (zoê) is self-motion; hence we see three modes of self-motion here. Artemis imparts animal motion, Hera imparts psychical motion, Demeter the motion of the cosmos as a whole. (I have to be a little vague here, because Sallustius, though using essentially the same categories Proclus does later, orders his classes a little differently. To get historical about it, Sallustius is probably abridging the system of Iamblichus here, an earlier form of the Platonic philosophy of religion that is still in use, with modifications, by Proclus in the 5th c. CE and right down to the closure of the Academy in Athens in the 6th c.)
The lifegiving function is more specific than the demiurgic function, though only subtly so; the final two functions Sallustius mentions, however, are more clearly ranged 'under' the prior two, that is, presupposing them. (No Gods are really 'above' or 'below' any others; some merely choose to act 'before' or 'after' certain others.) The 'harmonizing' function is essentially about applying the order of the dêmiourgoi to the motions of things that are in whole or in part moved by something else, because essential life is self-motion. Alter-motion, passive motion, is ordered, entrained, and these Gods are sources of this ordering, Apollo through music, prophecy, and healing; Aphrodite through beauty itself--her activity actually beginning well before the plane on which Sallustius mentions her here, as she is of the pre-Olympian generation--but here she is operating within the Olympian regime, and thus in the sphere of socialized beauty, especially the beauty of virtue; Hermes through divination and other 'hermetic' pursuits.
The 'guardian' function, finally, is about preventing entrainment of motion from sources contrary to the will. Thus the Kouretes, paradigmatic 'guardians' for the Platonic philosophy of religion, protect the infant Zeus so that the pattern of motion Zeus imparts to the cosmos will remain distinct from the Titanic pattern of his father Kronos. This means, ultimately, that the realm of ideas will have some independence from the realm of nature. In Sallustius' analysis (again, somewhat different from the Proclean one, so I have to do some educated guesswork here) Hestia tends the hearth of being itself, as guardian of the possible; Athena guards Zeus' order from forces that, while not evil in themselves, cannot have the last word, so to speak, if the fullness of manifestation is to be safeguarded (e.g., the Giants); while Ares guards the autonomy of forces on the plane of embodiment, where the outcome of conflict cannot be wholly predetermined by ideal factors (forces 'fight it out', so to speak).