A subjective interpretation though this is, it would seem that Robert Frobisher is in the throws of a manic episode, thus strongly indicating that he suffers from bipolar disorder. The sleeplessness, the obsessive drive towards a creative goal (to the exclusion of everything else including sex), his financial recklessness (why one of the most expensive hotels in Bruges?), his impetuousness, the expansive even imperial nature of his prose, his agitated and violent state when he confronts Eva - all serve to convince me that Frobisher is suffering from what is now a widely recognised form of mental illness. The cyclical nature of bipolar further widens the book's exploration of the theme of circularity (see below).
By all accounts devilishly tricky to translate, but might go something like 'there are tears for things'. This may seem a little arbitrary, but placed in its literary context it makes more sense. The phrase comes from Book I of Virgil's The Aenied in which the protagonist, whilst crying over murals of the war dead, utters some of the most resonant words in all world literature: "sunt lacrimae rerum et mentem mortalia tangunt". This has been translated as "The world is a world of tears, and the burdens of mortality touch the heart."
This notion of eternal return (i.e. the universe is infinitely recurring) has been explored in Ancient Egypt, Ancient Greece, in Hinduism and Buddhism as well as by European philosophers Arthur Schopenhauer and Friedriech Nietzche. In The Gay Science Nietzche asks
'What, if some day or night a demon were to steal after you into your loneliest loneliness and say to you: 'This life as you now live it and have lived it, you will have to live once more and innumerable times more' ... Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus? Or have you once experienced a tremendous moment when you would have answered him: 'You are a god and never have I heard anything more divine.'
The infinitely cyclical nature of existence is exemplified historically in the image of a dragon eating its own tail, a symbol that has itself been recycled by many cultures but can eventually be traced back to Ancient Egypt (circa 1600 BC).
All forms of sea bird. Mother Carey's Chickens are storm petrels, and Mother Carey an ancient nautical reference to the old crone who controlled inclement weather. The name petrel comes from the Latin name for Saint Peter, owing to the fact that hovering petrels appear to be walking on water. The 'purplish moths' were probably Othreis fullonia, which populate the South Pacific Islands and feed on fruit.