Any why is he such a dick?
Reinhard Kuhn (the author of The Demon of Noontide: Ennui in Western Literature) defined ennui as “the state of emptiness that the soul feels when it is deprived of interest in action, life, and the world (be it this world or another), a condition that is the immediate consequence of the encounter with nothingness, and has as an immediate effect a disaffection with reality.”
It is closely related to, co-exists with, boredom. In the words of Blaise Pascal: “Nothing is so insufferable to man as to be completely at rest, without passions, without business, without diversion, without study. He then feels his nothingness, his forlornness, his insufficiency, his dependence, his weakness, his emptiness. There will immediately arise from the depth of his heart weariness, gloom, sadness, fretfulness, vexation, despair.”
The earliest men to study ennui were the first generations of monks. Ennui accosted them fiercely, so much so that it was included in Evagrius' original list of capital sins. It was known by the monks as the “Demon of Noontide,” since it often struck between the hours of ten and two.
It seems that ennui accosts religious men fiercely because their souls forsake all worldly attachments, leaving them particularly vulnerable to ennui's attacks. When grace (that seemingly-capricious gift!) departs, it leaves them with no attachments, worldly or spiritual, with the result that their souls are tossed about in an ocean of despair, with nothing whatsoever to hold onto. It is not surprising that generations of monks have counseled gardening–a tangible, sink-your-hands-in-the-earth activity–as a good remedy for ennui.
The secular man also suffers from ennui, but of a different sort. When the grace of God leaves his soul, he still has the world's attractions to grab, and this helps stem ennui's assault. For the worldly man, these attractions (diversions) are imperative for warding off the Noontide Demon.
The diversions differ in degree. There are simple diversions and there are highly-engaging diversions. Simple diversions, like shopping and a round of golf, are effective for only a little while. They tend to lose their diverting ability quickly, leaving a person bored and susceptible to despair and ennui.
For this reason, fear of ennui has often driven people to more substantive pursuits. In Kuhn's words, it “is imperative that man be able to take his distractions seriously, for otherwise it would be impossible for him to give himself over to them wholeheartedly. Man has an overwhelming need to be convinced, if not of their importance, at least of their reality.”
This need to take diversions seriously has often pushed people to more important pursuits like art, literature, and charity work.
 Reinhard Kuhn, The Demon of Noontide: Ennui in Western Literature (Princeton University Press, 1976), p. 13.
 Pensees, No. 131. See 33 Great Books of the Western World, Pascal (Encyclopedia Brittanica, 1952), p. 195.
 Though many people squeez an incredible amount of diversion out of a simple pursuit, as evidenced by the extreme (some might say silly) seriousness people put on their hobbies.
 Kuhn, op. cit., p. 110.