[This is adapted from a dvar Torah given by one of my fellow students last night. He cited the Maharal of Prague and the Shem mi-Shumel for different parts of the whole, but I no longer remember which part went with whom, so just keep that in mind.]
At the end of this week's Torah portion, we see for the first time the family of Avram (who would later become Avraham, forefather of the Jewish people). The narrative speaks briefly of his brother Haran, saying only that he "died before the face of his father."
A well-established tradition expands on the narrative in the text to explain what happened. (While there is little evidence for the expanded version in the Torah itself, it is accepted as authoritative history by even the arch-rationalist Maimonides.) According to this tradition, King Nimrod had set up a cult of the god-king based around himself. Avram, having already reasoned out the existence of God, refused to worship Nimrod or any other idol and was thrown into a furnace in punishment. Haran was watching at the time, and not having Avram's faith was afraid to intervene. God saved Avram from death and eventually he was retrieved from the furnace.
At this point there are two variants. In one, Haran saw that Avram survived and immediately announced that he too would not worship Nimrod—at which point he too was thrown in the furnace, and was consumed in the fire. In the other variant, God strikes Haran down directly for his lack of faith, again with fire. In either case, Haran dies because he lacks true beliefs and just goes where the wind blows.
If you look at the three letters of his name, "hei reish nun," you find something interesting. The numerical value of "hei" is five, i.e. midway between one and ten (on the low side). The value of "nun" is fifty, i.e. midway between ten and a hundred (again on the low side). The value of "reish" is two hundred, midway between one hundred and four hundred (only four letters are valued in the hundredths-place).
Essentially, Haran was the ultimate example of mediocrity. His instinct was to converge on the center, with no other purpose than to avoid standing out in either direction. When it seemed that Nimrod was the ultimate power, Haran acquiesced to Nimrod's orders. When it seemed that Avram had bested Nimrod, Haran immediately switches over to Avram's side. But his inconstancy is his undoing and he ultimately perishes. But the story is not done.
According to a kabbalistic tradition, Aharon the Priest, brother of Moshe (Moses), was a gilgul of Haran. In simplistic terms, this means that Aharon's soul had the same "spiritual DNA" as that of Haran, and was sent to the world in part to rectify Haran's mistakes.
Aharon's name contains all the letters of Haran's name, with the additional letter "aleph." This implies that Aharon shared the same instinct towards the center that Haran did, with the difference that his centrism was dedicated towards the service of God (hence the aleph). Aharon was the great peacemaker of Israel, called by Hillel "a lover of peace and a pursuer of peace." He was especially known in the tradition for reconciling two good friends who had quarreled, or a husband and wife who had marital discord.
Several times in the Torah we see Aharon taking great risks to head off disaster. During the episode of the Golden Calf, Aharon acquiesces to the demands of the mob and actually facilitates their idolatry, but in such a way as to delay them and contain their lawlessness; in the end, the damage to the people was lessened by Aharon's actions and he was pardoned. In another instance, Aharon intercedes when God sets loose a plague amongst the people, and the plague is halted.
The difference between simple mediocrity and a true spirit of moderation, it seems, is that the mediocre man has no firm principles animating his conduct. His every action is geared towards his own advancement or self-preservation, with no higher aim. The true moderate, on the other hand, seeks to bring other people together for a higher purpose—in this case to serve God and to promote peace among the community. To do so he may take great risks, but they are always in order to increase fellowship and peace. May we see fewer examples of mediocrity, and more examples of true moderation motivated by the service of God and humanity.