Until the Renaissance, the work of Calcidius offered the medieval West almost the only direct access to Plato s corpus not dispersed in fragments. In the 4th century CE, Calcidius translated into Latin an important section of Plato s "Timaeus," complemented by extensive commentary and organized into coordinated parts. The first part is broadly devoted to the architecture of the world, to its intelligible structure. The second delves into the nature of the living creatures that inhabit it. This basic division subsequently informed the sense of macrocosm and microcosm of the world and our place in it which is prevalent in western European thought in the Middle Ages. At the same time, this medieval volume altered perspectives on Plato by drawing on other philosophical traditions, particularly the Stoic and Peripatetic, while including Judeo-Christian cosmology and anthropology. The present edition provides the first English translation of Calcidius s work."
Calcidius (or Chalcidius) was a 4th-century philosopher (and possibly a Christian) who translated the first part (to 53c) of Plato's Timaeus from Greek into Latin around the year 321 and provided with it an extensive commentary. This was likely done for Bishop Hosius of Córdoba. Very little is otherwise known of him.
His translation of the Timaeus was the only extensive text of Plato known to scholars in the Latin West for approximately 800 years. His commentary also contained useful accounts of Greek astronomical knowledge. In the 12th century commentaries on this work were written by Christian scholars including Hisdosus and philosophers of the Chartres School, such as Thierry of Chartres and William of Conches. Interpreting it in the light of the Christian faith, the academics in the School of Chartres understood the dialogue to refer to creation ex nihilo.
Along with Macrobius, Calcidius was one of the main sources for Platonism (or Neo-Platonism) in the West for hundreds of years. Until Marsilio Ficino translated all of Plato's works and other Platonist and Neo-Platonist works into Latin, there was very little available to Latin speaking thinkers. Of course, Aristotle did not suffer from that same lack of regard. And that unfortunately accounts for the pedantism of some of the scholastics.
Thanks largely to Macrobius and Calcidius, Platonism didn't completely vanish in the West during the dark ages. I was impressed with both Macrobius and Calcidius. They covered a lot of ground in their respective works. Some of it I was already familiar with; unlike the scholastics, I have access to adequate translations of Platonist writings, so I am pretty well acquainted already. Calcidius and Macrobius were the only real bridge to Platonist thought available to Western medieval philosophers. Of course, a lot of the Platonist material included here is in a number of different works, but one must remember that those works were in Greek and were not readily available during that time.
Calcidius is a bit of an anomaly. He composed this commentary for a bishop and that he was aware of his dedicatee's religious disposition is obvious, but his own religious disposition is a little less so. I think, however, that one can surmise, given the accumulated evidence found in here, that if Calcidius was a Christian, it was only nominally. The factors that suggest that he sided with Platonism against Christian thought is apparent in his belief in 1) the eternity of the world; 2) the divinity of the luminaries; 3) the goodness of some daemons; 4) evil being correspondent with matter, and possibly in other points he presents. In some of these cases he is contextually relating Platonist views, but he does give clues when he is in agreement with them. He mentions Jewish thought in passing and usually in regards to the disposition of his addressee. He only refers to the New Testament once and only in passing. He doesn't quote Plotinus, Porphyry or Iamblichus and there seems to be no internal evidence that suggests that he was even aware of them, let alone read them. The only Platonist thinker he quotes repeatedly is Numenius. This is interesting. Numenius and Ammonius Saccas were the immediate predecessors of Plotinus and he was influenced by both. Numenius was a Platonist Neo-Pythagorean with semi-gnostic tendencies. Numenius was strongly influenced by Philo of Alexandria as well. Numenius was noted by the Church Fathers for saying that Plato was a Moses who spoke Attic Greek. Numenius was not apprehensive about developing a syncretic philosophical system where he could adapt ideas from Plato, Christianity, Judaism, Gnosticism, and maybe from other systems, that appealed to him. It is my personal belief that Calcidius was a Numenian and probably had no problem accepting certain aspects of Judaism and Christianity when it didn't conflict with his Platonist disposition. He could probably claim enough of Christian thought to be a palatable source for Christian thinkers during this time; in a way that Porphyry definitely could not. Being a Numenian would make him a lot more religiously conciliatory. But, on the other hand, it makes him a lot more ambiguous and ambivalent.
Both Calcidius and Macrobius spend some amount of time discussing cosmological questions. Macrobius spends more time on dream interpretation and Calcidius spends more time discussing matter and the origin of evil. Both of them discuss questions regarding fate and related philosophical issues.
I do strongly recommend Calcidius' commentary on the Timaeus and Macrobius' commentary on the Dream of Scipio. Both were incredibly influential on Western thought for quite a long time. In my opinion, any criticism relating to originality are completely irrelevant and can be safely ignored. These works were far more interesting than most of the Aristotelian plagiarists of the period and they also have the benefit of being incredibly lucid when discussing Platonic issues, which means that almost anyone can read them and understand them well enough.
I should add that this edition contains both the Latin and English translation: Latin on the left page and translation on the right. John Magee provides some useful notes as an appendix as well. Harvard University Press and John Magee should be commended for this edition. It really should have been translated into English a long time ago.