Hubris is the “extreme haughtiness or arrogance” that “often indicates being out of touch with reality and overestimating one’s own competence or capabilities, especially for people in positions of power.”
Wikipedia goes on: “Hubris, though not specifically defined, was a legal term and was considered a crime in classical Athens. It was also considered the greatest crime of the ancient Greek world. The category of acts constituting hubris for the ancient Greeks apparently broadened from the original specific reference to mutilation of a corpse, or a humiliation of a defeated foe, or irreverent “outrageous treatment” in general. It often resulted in fatal retribution or Nemesis. Atë, ancient Greek for “ruin, folly, delusion,” is the action performed by the hero, usually because of his/her hubris, or great pride, that leads to his/her death or downfall.” Then this: “Perhaps one of the most vivid examples of hubris in ancient Greek literature is demonstrated by Achilles and his treatment of Hector’s corpse in Homer’s Iliad. Achilleskilled Hector in revenge. Not only did he kill him, but he stripped Hector’s corpse and dragged it around behind his chariot, threading leather thongs through Hector’s ankles. Although the Greek forces were appalled by his treatment of this other hero’s corpse, he was unrelenting. Priam, king of Troy, had to come and kneel at Achilles’s feet and offer him Hector’s weight in gold before he could convince him to give up the body. Once the body was gone, Achilles had time to ponder the fact that it was prophesied his own death would come soon after Hector’s.” And that is the point. Hubris is the change in personality and ego that by its very definition comes before, and is the direct cause of, the fall. The Ancient Greek’s new this and had a mechanism to limit or prevent hubris: deities. For it was the fear of insulting or displeasing the Gods, and its potential repercussions, that kept the Greeks in check; one only needs to read the very first line of Homer’s The Iliad to see this. Today the likes of Apollo and Zeus have been relegated to cartoon or mythology. They have been replaced by the one true God in monotheistic religions. It is a shame that more people do not fear displeasing this one God as the Ancient Greeks feared displeasing their many.