One of the key innovations of later Neoplatonism was the concept of series or chains (seirai, sg. seira), based on the Homeric image of the golden chain. In the Iliad 15.23–25, Zeus threatens Hera by reminding her of the time he suspended her from a chain of gold, with iron anvils tied to her feet. Earlier philosophers had explained this as a reference to the creator god (Zeus) and his hierarchical ordering of the cosmos: Fire, containing the brilliant stars, at the top (golden chain), then Air (Hera), and then the two heavy elements, Water and Earth (the two anvils). The later Neoplatonists, however, generalized the idea. For them, there was not only one series passing from the demiurge through the elements, or (as in Plotinus) a unitary line of emanation from the One through Intellect to Soul and the cosmos, but many distinct chains running from high points in the metaphysical system to lower ones, often passing through different classes or orders (taxeis, sg. taxis) of beings.
One result of this innovation was that the Platonic framework, albeit still monistic and hierarchical, could now encompass a multitude of interacting hierarchies, and was thus able to incorporate a broad range of theological traditions without reducing them to one predetermined system. Let us compare Plotinus of Lycopolis, the originator of what we now call Neoplatonism, and Proclus the Lycian, the most prominent expositor of later Neoplatonism. The former, in his treatise on Eros (see esp. Ennead 3.5.8), struggles to make mythology conform to his system of the three hypostases (One, Intellect, Soul). In the succession of kingship among the gods as Hesiod narrates it, Ouranos is succeeded by his son Kronos, and he in turn by his son, Zeus. Plotinus equates Ouranos with the One and Kronos with Intellect, but has previously identified Aphrodite with Soul. This leaves no room for Zeus, the son of Kronos and father of Aphrodite, so that he is forced to also equate Zeus with Intellect, or at least an intellect, and to declare Aphrodite the soul of Zeus. This connection, he says, is confirmed by the tradition of calling the planet Venus by two names, ‘star of Aphrodite’ and ‘star of Hera’. Proclus, on the other hand, does not need to conflate either Zeus with Kronos or Aphrodite with Hera, nor again to identify any god with the hypostases (the One itself, Intellect itself, Soul itself). Instead, he proposes a unique “kingly series”, drawn not only from Hesiod but especially from Orpheus, running as follows: Phanes, Nyx, Ouranos, Kronos, Zeus, Dionysus. This series is, in a sense, self-contained and does not impinge on the genealogical relationship between Zeus and Aphrodite.
Other series discussed by the Platonic philosophers are rooted not in a function, like kingship, but in a deity. So, for example, Hera and Aphrodite, whom Plotinus seems to conflate into one goddess, each fundamentally have their own divinity (theotēs) and their own series. Again, comparing Proclus against Plotinus is insightful, and here we can quote the Lycian’s own words:
“Some call (the Earth) Demeter, because they attribute the fertile (power) to it, like Plotinus (Enneads 4.4.27), who calls (the Earth’s) intellect Hestia, and her soul Demeter. We, however, say that the first causes of these goddesses are (all) intellective, hegemonic and absolute, and that there is a Chthonic (‘earthly’) Demeter and a Chthonic Hestia and Isis just as there is a Chthonic Zeus and Chthonic Hermes. These chthonic (gods) are all arranged around the one divinity of Earth (Gē = Chthōn), in the same way that the multitude of celestial (ouranioi) gods has advanced around the one divinity of Heaven (Ouranos). For the processions of all the gods in Heaven have terminated in the Earth, and all things that are in Heaven celestially are in the Earth chthonically. For the intelligible Earth also receives all paternal powers of Ouranos, and possesses them all productively.
“So, we also say that there is a Chthonic Dionysus and Chthonic Apollon, who brings forth the divinatory waters across the Earth, and the cavities that prophesy the future. (Apollon’s) Paeonic and judicial powers which have descended into her also make other places of the Earth purificatory, judicial or healing. But it is impossible to go through all the chthonic powers, because the divine (powers) cannot be circumscribed, and the orders of angels and daemons which follow each of them are still more. (These orders) have been allotted the whole Earth in a circle, and they dance around her one divinity, her one intellect and her one soul.” (Proclus, On the Timaeus vol. 3, p. 140)
As this passage indicates, the system is more complex than a grid consisting only of series and classes. Firstly, classes themselves cut across the ontological system. Gods, for example, are fundamentally at the level of divinity, daemons are intellects, humans are souls, and rocks are bodies; yet gods also have divine intellects, souls and bodies (which are the most perfect intellects, souls and bodies); daemons have daemonic souls and bodies; and humans have human bodies, which are superior to rocks.
Secondly, series intersect, but not equally at all ontological levels, but at specific points in specific ways. We may trace this back to the fact that the gods themselves, the origins of the series, are not entirely homogeneous but rather a “divine series” proceeding in a certain order from the first cause, the One itself (Proclus, Elements of Theology 113), and that their unique characters structure the ontological order that springs from them. Consequently, the powers of Earth and Heaven are not fully engulfed in each other, but rather, the Earth is present in Heaven celestially (through her powers, and perhaps also in more substantial ways), and Heaven in Earth chthonically, but still, Heaven is above Earth in the spatial/hierarchical order of the cosmos.